By Paul Reynolds
World Affairs correspondent BBC News website
Kim Jong-il expected to retain nuclear weapons capability
The return of international nuclear inspectors to North Korea is an important step forward in containing Pyongyang's nuclear programme, but it is not the end of that effort.
The inspectors, from the UN's nuclear supervisory body the International Atomic Energy Agency (IAEA), are to monitor the North's compliance with an agreement reached by six-party talks in February.
In that agreement, North Korea said it would "shut down and seal for the purpose of eventual abandonment" its nuclear facility at Yongbyon, which is capable of producing enough plutonium for a nuclear weapon each year.
However, the North's leader Kim Jong-il did not agree to give up any nuclear weapons he might have.
North Korea is estimated to have enough plutonium for between one and three weapons, according to the Washington think tank the Nuclear Threat Initiative, and it tested one device last October.
North Korea remains outside the Nuclear Non-Proliferation Treaty, which restricts the spread of nuclear weapons.
There are serious doubts that it will give up its weapons capability in the foreseeable future. Further talks are due to take place about this under the heading of the "Denuclearization of the Korean Peninsula".
Game plan unclear
"The despatch of the IAEA inspectors is only the first step in what will be a long, arduous process for which the final steps have not even been agreed," said Mark Fitzpatrick, nuclear watcher at the International Institute for Strategic Studies in London.
"Shutting down Yongbyon is easy for the North Koreans. They did it before under the 1994 agreement with President Clinton and then restarted it in 2002, but getting inspectors in is an important demonstration of progress.
"Nobody really knows North Korea's game plan. But it is getting rewards for this move - the relaxation of financial restrictions on the bank in Macau it has been using for its counterfeiting and other activities and the provision of large amounts of fuel oil."
South Korea is about to send 50,000 tons of fuel oil, an event expected to prompt the North Koreans actually to shut down the Yongbyon plant.
"For Washington, the benefit is that this demonstrates that the crisis in being managed," Mark Fitzpatrick added.
"However we should not have a false sense of optimism and I do not think that North Korea will ever agree to give up nuclear weapons without a change in its security set-up."
The progress over North Korea is in contrast to the impasse with Iran, which is developing an expertise in enriching uranium - the other route, apart from plutonium, to a nuclear bomb.
Iran has rejected a proposal from the EU negotiator Javier Solana for a "double freeze".
Under this proposal, there would be no further sanctions on Iran and Iran would not install any more enrichment centrifuges while talks were held about further substantive negotiations, which would include the United States.
Because of these protracted talks about talks, there is now little expectation that the Security Council will consider further sanctions on Iran until September, after the summer break.
The only ray of hope for progress is a report by the IAEA that Iran has slowed down its work on centrifuges, but the significance or otherwise of this is not known yet.