A team of UN nuclear inspectors will soon be allowed to visit a North Korean reactor at the centre of a key disarmament deal, reports say.
N Korea has pledged to shut down its main reactor at Yongbyon
It will be the first international monitoring team to be given access to the Yongbyon reactor since 2002.
Analysts say the move shows the North Koreans are serious about a pledge to "shut down and seal" the reactor.
But in a sign the North remains anxious to prove its bargaining power, it has reportedly tested another missile.
Yonhap news agency reported that the short-range missile was fired early on Wednesday morning towards the waters off the Korean peninsula's east coast.
If confirmed, it would be the fourth missile the North has tested since the beginning of May.
The leader of the UN's International Atomic Energy Agency (IAEA) team, Olli Heinonen, told Japan's Kyodo news agency: "We're going to Yongbyon."
He added that the four-person IAEA team would go to the facility on Thursday and return to Pyongyang, where they are currently holding meetings, on Friday.
N KOREA NUCLEAR DEAL
N Korea to "shut down and seal" Yongbyon reactor, then disable all nuclear facilities
In return, will be given 1m tons of heavy fuel oil
N Korea to invite IAEA back to monitor deal
Under earlier 2005 deal, N Korea agreed to end nuclear programme and return to non-proliferation treaty
N Korea's demand for light water reactor to be discussed at "appropriate time"
IAEA monitoring officials were expelled from Yongbyon in December 2002, after which the reactor went into operation, allegedly producing enough plutonium for several nuclear devices.
But under an international deal agreed in February, the North agreed to "shut down and seal" the reactor in exchange for international aid.
While news of a possible return visit is an important step forward towards implementation of the deal, questions remain over the level of access the inspectors will be given.
The Yongbyon plant, about 100km (65 miles) north of Pyongyang, is thought to be a heavily guarded area defended by anti-aircraft positions, and the compound houses over 100 buildings.
A European Union delegation has also recently visited Pyongyang, and returned voicing optimism that the North Koreans were serious about nuclear decommissioning.
EU parliamentarian Hubert Pirker - part of a group that returned to South Korea from the North on Wednesday - said Pyongyang officials were positive about relations with the US and the international community.
The South Korean foreign minister also sounded a positive note on Wednesday, predicting a short timescale for the closure of Yongbyon.
"After the consultation is over, I think it will be shut down as early as possible," said Song Min-soon.
Pyongyang officials had also expressed interest in expanding economic ties with the EU, on building hydro-electric power stations, developing light industry and improving food production, Mr Pirker said.
The various visits to North Korea this week became possible after a long-running row between the US and North Korea was finally resolved.
Progress on the February disarmament deal ground to a halt due to a dispute over North Korean funds that were frozen in a Macau bank under US-instigated sanctions.
The North refused to make any progress on the deal until it had access to the money.
But after weeks of negotiations, Pyongyang said on Monday that it had finally received its $25m (£12.5m) funds, and confirmed it would therefore proceed to close down Yongbyon.
South Korea said on Tuesday that it would resume food aid to the impoverished North, now that the dispute was over.