These are the key events in the long-running crisis over North Korea's nuclear weapons ambitions.
3-5 October 2002: On a visit to the North Korean capital Pyongyang, US Assistant Secretary of State James Kelly presses the North on suspicions that it is continuing to pursue a nuclear energy and missiles programme.
Mr Kelly says he has evidence of a secret uranium-enriching programme carried out in defiance of the 1994 Agreed Framework.
Under this deal, North Korea agreed to forsake nuclear ambitions in return for the construction of two safer light water nuclear power reactors and oil shipments from the US.
16 October: The US announces that North Korea admitted in their talks to a secret nuclear arms programme.
17 October: Initially the North appears conciliatory. Leader Kim Jong-il says he will allow international weapons inspectors to check that nuclear facilities are out of use.
18 October: Five Japanese citizens abducted by North Korea 25 years before are allowed a brief visit home - but end up staying, provoking more tension in the region.
20 October: North-South Korea talks in Pyongyang are undermined by the North's nuclear programme "admission".
US Secretary of State Colin Powell says further US aid to North Korea is now in doubt.
The North adopts a mercurial stance, at one moment defiantly defending its "right" to weapons development and at the next offering to halt nuclear programmes in return for aid and the signing of a "non-aggression" pact with the US.
It argues that the US has not kept to its side of the Agreed Framework, as the construction of the light water reactors - due to be completed in 2003 - is now years behind schedule.
14 November: US President George W Bush declares November oil shipments to the North will be the last if the North does not agree to put a halt to its weapons ambitions.
18 November: Confusion clouds a statement by North Korea in which it initially appears to acknowledge having nuclear weapons. A key Korean phrase understood to mean the North does have nuclear weapons could have been mistaken for the phrase "entitled to have", Seoul says.
11 December: North Korean-made Scud missiles are found aboard a ship bound for Yemen, provoking American outrage.
The US detains the ship, but is later forced to allow the ship to go, conceding that neither country has broken any law.
12 December: The North threatens to reactivate nuclear facilities for energy generation, saying the Americans' decision to halt oil shipments leaves it with no choice. It blames the US for wrecking the 1994 pact.
13 December: North asks the UN's International Atomic Energy Agency (IAEA) to remove seals and surveillance equipment - the IAEA's "eyes and ears" on the North's nuclear status - from its Yongbyon power plant.
22 December: The North begins removing monitoring devices from the Yongbyon plant.
24 December: North Korea begins repairs at the Yongbyon plant.
North-South Korea talks over reopening road and rail border links, which have been struggling on despite the increased tension, finally stall.
25 December: It emerges that North Korea had begun shipping fuel rods to the Yongbyon plant which could be used to produce plutonium.
26 December: The IAEA expresses concern in the light of UN confirmation that 1,000 fuel rods have been moved to the Yongbyon reactor.
27 December: North Korea says it is expelling the two IAEA nuclear inspectors from the country. It also says it is planning to reopen a reprocessing plant, which could start producing weapons grade plutonium within months.
6 January: The IAEA passes a resolution demanding that North Korea readmit UN inspectors and abandon its secret nuclear weapons programme "within weeks", or face possible action by the UN Security Council.
7 January: The US says it is "willing to talk to North Korea about how it meets its obligations to the international community". But it "will not provide quid pro quos to North Korea to live up to its existing obligations".
10 January: North Korea announces it will withdraw from the Nuclear Non-Proliferation Treaty.
28 January: In his annual State of the Union address, President Bush says North Korea is "an oppressive regime [whose] people live in fear and starvation".
29 January: North Korea says Mr Bush's speech is an "undisguised declaration of aggression to topple the DPRK system" and dubs him a "shameless charlatan".
31 January: Unnamed American officials are quoted as saying that spy satellites have tracked movement at the Yongbyon plant throughout January, prompting fears that North Korea is trying to reprocess plutonium for nuclear bombs.
5 February: North Korea says it has reactivated its nuclear facilities and their operations are now going ahead "on a normal footing".
12 February: The IAEA finds North Korea in breach of nuclear safeguards and refers the matter to the UN security council.
24 February: North Korea fires a missile into the sea between South Korea and Japan.
25 February: Roh Moo-hyun sworn in as South Korean president.
2 March: Four North Korean fighter jets intercept a US reconnaissance plane in international air space and shadow it for 22 minutes.
10 March: North Korea fires a second missile into the sea between South Korea and Japan in as many weeks.
1 April: The US announces that "stealth" fighters sent to South Korea for a training exercise are to stay on once the exercises end.
9 April: The United Nations Security Council expresses concern about North Korea's nuclear programme, but fails to condemn Pyongyang for pulling out of the Nuclear Non-proliferation Treaty.
12 April: In a surprise move, North Korea signals it may be ready to end its insistence on direct talks with the US, announcing that "if the US is ready to make a bold switchover in its Korea policy for a settlement of the nuclear issue, [North Korea] will not stick to any particular dialogue format".
18 April: North Korea announces that it has started reprocessing its spent fuel rods. The statement is later amended to read that Pyongyang has been "successfully going forward to reprocess" the rods.
23 April: Talks begin in Beijing between the US and North Korea, hosted by China. The talks are led by the US Assistant Secretary of State for East Asian affairs, James Kelly, and the deputy director general of North Korea's American Affairs Bureau, Li Gun.
24 April: American officials say Pyongyang has told them that it now has nuclear weapons, after the first direct talks for months between the US and North Korea in Beijing end a day early.
2 May: Australian Foreign Minister Alexander Downer expresses concern after an official from North Korea's ruling Worker's Party is found on board a state-owned ship accused of bringing A$80m (US$50m) worth of heroin into Australia.
12 May: North Korea says it is scrapping a 1992 agreement with the South to keep the peninsula free from nuclear weapons - Pyongyang's last remaining international agreement on non-proliferation.
2 June: A visiting delegation of US congressmen led by Curt Weldon says North Korean officials admitted the country had nuclear weapons had "just about completed" reprocessing 8,000 spent fuel rods which would allow it to build more.
9 June: North Korea says publicly that it will build a nuclear deterrent, "unless the US gives up its hostile policy".
13 June: South Korea's Yonhap news agency says North Korean officials told the US on 30 June that it had completed reprocessing the fuel rods.
9 July: South Korea's spy agency says North Korea has started reprocessing a "small number" of the 8,000 spent nuclear fuel rods at Yongbyon.
1 August: North Korea agrees to six-way talks on its nuclear programme, South Korea confirms. The US, Japan, China and Russia will also be involved.
27-29 August: Six-nation talks in Beijing on North Korea's nuclear programme. The meeting fails to bridge the gap between Washington and Pyongyang. Delegates agree to meet again.
2 October: North Korea announces publicly it has reprocessed the spent fuel rods.
16 October: North Korea says it will "physically display" its nuclear deterrent.
30 October: North Korea agrees to resume talks on the nuclear crisis, after saying it is prepared to consider the US offer of a security guarantee in return for ending its nuclear programme.
21 November: Kedo, the international consortium formed to build 'tamper-proof' nuclear power plants in North Korea, decides to suspend the project.
9 December: North Korea offers to "freeze" its nuclear programme in return for a list of concessions from the US. It says that unless Washington agrees, it will not take part in further talks.
The US rejects North Korea's offer. President George W Bush says Pyongyang must dismantle the programme altogether.
An unofficial US team visits what the North calls its "nuclear deterrent" facility at Yongbyon.
22 January: US nuclear scientist Siegfried Hecker tells Congress that the delegates visiting Yongbyon were shown what appeared to be weapons-grade plutonium, but he did not see any evidence of a nuclear bomb.
23 May: The UN atomic agency is reported to be investigating allegations that North Korea secretly sent uranium to Libya when Tripoli was trying to develop nuclear weapons.
23 June: Third round of six nation talks held in Beijing, with the US making a new offer to allow North Korea fuel aid if it freezes then dismantles its nuclear programmes.
2 July: US Secretary of State Colin Powell meets the North Korean Foreign Minister, Paek Nam-sun, in the highest-level talks between the two countries since the crisis erupted.
23 August: North Korea describes US President George W Bush as an "imbecile" and a "tyrant that puts Hitler in the shade", in response to comments President Bush made describing the North's Kim Jong-il as a "tyrant".
28 September: North Korea says it has turned plutonium from 8,000 spent fuel rods into nuclear weapons. Speaking at the UN General Assembly, Vice Foreign Minister Choe Su-hon said the weapons were needed for "self-defence" against "US nuclear threat".
14 January: North Korea says it is willing to restart stalled talks on its nuclear programme, according to the official KCNA news agency.
19 January: Condoleezza Rice, President George W Bush's nominee as secretary of state, identifies North Korea as one of six "outposts of tyranny" where the US must help bring freedom.
10 February: North Korea says it is suspending its participation in the talks over its nuclear programme for an "indefinite period", blaming the Bush administration's intention to "antagonise, isolate and stifle it at any cost". The statement also repeats North Korea's assertion to have built nuclear weapons for self-defence.
18 April: South Korea says North Korea has shut down its Yongbyon reactor, a move which could allow it to extract more fuel for nuclear weapons.
1 May: North Korea fires a short-range missile into the Sea of Japan, on the eve of a meeting of members of the international Non-Proliferation Treaty.
11 May: North Korea says it has completed extraction of spent fuel rods from Yongbyon, as part of plans to "increase its nuclear arsenal".
16 May: North and South Korea hold their first talks in 10 months, with the North seeking fertiliser for its troubled agriculture sector.
25 May: The US suspends efforts to recover the remains of missing US servicemen in North Korea, saying restrictions placed on its work were too great.
22 June: North Korea requests more food aid from the South during ministerial talks in Seoul, the first for a year.
9 July: North Korea says it will rejoin nuclear talks, as US Secretary of State Condoleezza Rice begins a tour of the region.
12 July: South Korea offers the North huge amounts of electricity as an incentive to end its nuclear weapons programme.
25 July: Fourth round of six-nation talks begins in Beijing.
7 August: The talks reach deadlock and a recess is called.
13 September: Talks resume, but a new North Korean request to be built a light water reactor prompts warnings of a "standoff" between the parties.
19 September: In what is initially hailed as an historic joint statement, North Korea agrees to give up all its nuclear activities and rejoin the nuclear Non-Proliferation Treaty, while the US says it had no intention of attacking.
20 September: North Korea says it will not scrap its nuclear programme until it is given a civilian nuclear reactor, undermining the joint statement and throwing further talks into doubt.
11 November: Fifth round of six-nation talks ends without progress.
7 December: A senior US diplomat brands North Korea a "criminal regime" involved in arms sales, drug trafficking and currency forgery.
20 December: North Korea says it intends to resume building nuclear reactors, because the US had pulled out of a key deal to build it two new reactors.
12 April: A two-day meeting aimed at persuading North Korea to return to talks on its nuclear programme fails to resolve the deadlock.
3 July: Washington dismisses a threat by North Korea that it will launch a nuclear strike against the US in the event of an American attack, as a White House spokesman described the threat as "deeply hypothetical".
4 July: North Korea test-fires at least six missiles, including a long-range Taepodong-2, despite repeated warnings from the international community.
5 July: North Korea test-fires a seventh missile, despite international condemnation of its earlier launches.
7 July: South Korea suspends food aid in protest at the missile tests.
15 July: The UN Security Council unanimously votes to impose sanctions on North Korea over the missile tests. The resolution demands UN members bar exports and imports of missile-related materials to North Korea and that it halt its ballistic missile programme.
11 September: Senior US diplomat Christopher Hill warns North Korea against a nuclear test, saying that it would be a provocative act.
27 September: North Korea blames US financial sanctions for the deadlock in multilateral talks on its nuclear programme. In a speech to the UN General Assembly, envoy Choe Su-Hon said that North Korea was willing to hold talks, but the US stance had created an impasse.
3 October: North Korea is to conduct a nuclear test to "bolster" its self-defence in the face of US military hostility, the foreign ministry says. In a statement, it says North Korea would carry out the test "in the future... where safety is firmly guaranteed" - but did not say when.
9 October: North Korea says it has carried out its first ever test of a nuclear weapon. It calls the test a "historic event" and says it was carried out safely and successfully.
14 October: The UN Security Council votes unanimously to impose weapons and financial sanctions on North Korea over its claimed nuclear test. Resolution 1718 demands that North Korea eliminate all its nuclear weapons, weapons of mass destruction and ballistic missiles.
The resolution allows nations to inspect cargo moving in and out of North Korea to check for non-conventional weapons but is not backed by the threat of force. It also calls for Pyongyang to return "without precondition" to stalled six-nation talks on its nuclear programme.
16 October: US intelligence officials announce that air samples gathered from the test site contain radioactive materials which confirm that North Korea carried out an underground nuclear explosion. The size of the blast was less than 1 kiloton, the statement says.
31 October: China announced that six nation talks will resume "soon", following a meeting between envoys from the US, North Korea and China.
18 December: Six-nation talks resume in Beijing.
22 December: Talks end with no sign of progress.
29 December: South Korea describes its northern neighbour as a "serious threat", in the wake of its nuclear test in October
9 January: Japan's PM Shinzo Abe tells the BBC his country cannot tolerate a nuclear-armed North Korea and calls for closer international co-operation to stop such an outcome.
8 February: Six-nation nuclear talks resume in Beijing.
13 February: North Korea agrees to take the first steps towards nuclear disarmament, as part of a deal reached during talks.
23 February: The head of the UN's nuclear agency, Mohamed ElBaradei, says he has been invited to North Korea for talks on its nuclear programme.
13 March: Mohamed ElBaradei goes to Pyongyang for talks. He says North Korea is "fully committed" to giving up its nuclear programme.
15 March: The US ends an inquiry into the Macau-based Banco Delta Asia, paving the way for a block on North Korea's accounts, containing $25m (£13m), to be lifted.
22 March: Six-party talks to discuss progress on the 13 February deal stumble after Pyongyang says it is unable to access its funds in a Macau bank.
14 April: North Korea misses the deadline to "shut down and seal" its Yongbyon nuclear reactor in exchange for energy aid, saying the banking row first needs to be resolved.
12 June: Russia offers to facilitate the fund transfer.
21 June: US nuclear envoy Christopher Hill arrives for a surprise visit to Pyongyang.
25 June: North Korea confirms it has received the funds.
26 June: IAEA inspectors arrive in North Korea, the first time they have been allowed into the country since 2002.
14 July: North Korea tells the US it has shut down its nuclear reactor after receiving the first shipments of heavy fuel oil. IAEA inspectors arrive for a monitoring visit to Yongbyon.
16 July: International inspectors confirm North Korea has shut down Yongbyon.
2 September: Following bilateral talks in Geneva, the US says Pyongyang has agreed to declare and disable all its nuclear facilities by the end of the year.
3 September: North Korea says Washington has agreed to take it off a list of countries that sponsor terrorism.
3 October: Chinese officials say North Korea has agreed to disable its nuclear facilities at Yongbyon and give complete details of its nuclear programme by 31 December.
11 October: A team of nuclear experts arrives in North Korea to oversee the dismantling of reactors and other facilities.
6 November: US nuclear experts say they have made a "good start" disabling the reactor.
4 December: The top US envoy to North Korea, Christopher Hill, makes a rare visit for talks with the country's foreign minister. After visiting the Yongbyon facility, he says progress on disabling it is "going well".
6 December: US President Bush sends a letter to Kim Jong-il urging him to follow through on North Korea's pledge to reveal full details of its nuclear programme.
31 December: North Korea fails to meet a deadline to disclose full details of its nuclear programme by the end of 2007.
7 January: US nuclear envoy Christopher Hill call for patience towards North Korea and says that the US is ready to persevere with negotiations in order to secure a complete and correct declaration.
31 Jan: North Korea has not changed its mind about ending its nuclear programme, Kim Jong-il reportedly says.
19 February: US and North Korean nuclear negotiators hold talks in Pyongyang, but no deal is reached.
26 Feb: The New York Philharmonic performs a groundbreaking concert in North Korea, seen as a major act of cultural diplomacy.
28 March: North Korea test-fires short-range missiles off its western coast.
8 April: US and North Korean negotiators hold more talks in Singapore; both say progress was made.
25 April: The US accuses North Korea of helping Syria build a nuclear reactor that "was not intended for peaceful purposes"; US says it is concerned about Pyongyang's "proliferation activities".
13 May: North Korea hands over documents concerning its plutonium production programme.
26 June: After a delay of more than six months, the North hands over an account of its nuclear programme, enabling six-party negotiations to restart on 10 July.
27 June: North Korea demolishes the cooling tower at its Yongbyon nuclear reactor, in a symbol of its commitment to the talks on ending its nuclear programme.
24 July: The US Secretary of State Condoleezza Rice meets her North Korean counterpart, Foreign Minister Pak Ui-chun, for informal talks at an Asean summit in Singapore - the first such meeting for four years. Ms Rice says the talks are "good", with no surprises.
26 August: Two months after submitting its nuclear declaration, Pyongyang says it has stopped disabling its nuclear facilities in protest at the US failure to remove it from its list of state sponsors of terrorism.
24 September: The UN's nuclear watchdog, the IAEA, says North Korea has removed seals preventing it using its main plant at Yongbyon. North Korean officials say UN inspectors will have no further access to the plant.
9 October: The UN's nuclear watchdog says North Korea has banned its inspectors from entering the Yongbyon nuclear complex.
11 October: The US says it has taken North Korea off its list of state sponsors of terrorism, after North Korea agrees to full verification of its nuclear sites.
10 December: Latest round of six-party talks ends without agreement on how to verify North Korea's account of its atomic activity.
24 February 2009: North Korea announces that it is preparing to launch a satellite, Kwangmyongsong-2, from its north-eastern coast.
5 April 2009: The rocket is launched at 0230 GMT to international condemnation. It flies over Japan and lands in the Pacific Ocean. The launch is widely viewed as a pretext to test a type of missile capable of carrying a nuclear warhead.
14 April 2009: North Korea announces that it will pull out of the six-party talks and orders IAEA inspectors to leave the Yongbyon complex and the country in response to UN Security Council criticism of its recent rocket launch.
25 May 2009: North Korea detonates an underground nuclear explosive device. This is North Korea's second nuclear test and is believed to be several times more powerful than the first one tested in 2006.
26 May 2009: North Korea test-fires two short-range missiles hours after the UN Security Council condemns the nuclear test.
27 May 2009: North Korea says it will no longer guarantee the safety of US and South Korean vessels off its south-western coast and is no longer bound by the truce that ended the 1950-53 Korean War.
12 June 2009: The UN Security Council votes unanimously to impose tougher sanctions on North Korea. Pyongyang responds by saying it will view any US-led attempt to blockade the country as an "act of war" and that it plans to "weaponise" its plutonium stocks and start enriching uranium.
30 June 2009: South Korea confirms that the North is going ahead with its threat to enrich uranium, which can be used to fuel a nuclear reactor, or be more highly-enriched for use in a nuclear weapon.
5 August 2009: Former US President Bill Clinton visits to help secure the release of two detained US journalists.
6 October 2009: North Korea tells China it may be willing to return to six-party talks, if it sees progress in bilateral talks with the US.