The agreement, made during six-nation talks, offers the North aid, security guarantees and better diplomatic standing in return for abandoning its nuclear programme.
North Korea ejected International Atomic Energy Agency officials in December 2002 shortly before it announced it was leaving the nuclear Non-Proliferation Treaty.
"North Korea has only one card in hand and that is its nuclear programme"
Rahy, Tehran, Iran
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South Korea meanwhile has said that following the North's agreement to proceed with the nuclear shutdown, it will resume food aid deliveries to the North at the end of the month.
Eventually, it says, some 400,000 tonnes of rice will be shipped.
Seoul suspended food aid after Pyongyang defied international warnings and test-fired a barrage of missiles in July 2006.
Arriving in Pyongyang on Tuesday morning, Olli Heinonen, the head of the IAEA team, said his delegation would be "negotiating arrangements for verification of the shutdown and sealing'' of the Yongbyon reactor during the five-day trip.
On February 13, 2007, at six-nation talks in Beijing, North Korea agreed to:
Start shut down of main Yongbyon nuclear reactor facility within 60 days of deal
Allow UN nuclear inspectors entry for all monitoring and verification
Discuss list of all nuclear programmes and materials including plutonium extracted from fuel rods
Declare all nuclear programmes and disarmament of all existing nuclear facilities
Begin talks on normalising diplomatic ties with the US and Japan, and resume high-level talks with South Korea
In return US, Russia, China, Japan and South Korea promise initial shipment of 50,000 tonnes heavy fuel oil within initial phase
The five nations agreed to establish working groups for initial and full implementation of action plan
Additional aid up to the equivalent of 1m tonnes of heavy fuel oil to be delivered to North Korea upon compliance
He said it would be largely up to the North Koreans to decide how long it would take, but he said North Korean officials gave his delegation a friendly reception at the airport and appeared ready for discussions.
"It seems to be a good start," he told The Associated Press in a telephone interview.
Under the February agreement, North Korea will receive an initial 50,000 tonnes of fuel for closing the Yongbyon facility, and a total of one million tonnes when its nuclear programmes are fully dismantled.
On Monday, North Korea confirmed that it had finally received about $25m in funds that had been frozen in a Macau bank.
The row over the funds, which the US had earlier said were connected to North Korean money-laundering and counterfeiting operations, had been a major roadblock to the disarmament deal.
But despite making progress on the nuclear issue, North Korea has made clear it is not prepared to ease up on criticism of its neighbours.
On Tuesday its embassy in Beijing summoned reporters to a rare press conference where they introduced a woman who claimed she had been abducted to Japan, where she has lived since 2003.
Al Jazeera's Beijing correspondent, Melissa Chan, says the display is sure to provoke annoyance in Tokyo, which has worked hard to free its own citizens kidnapped by North Korean agents in the 1970s.
Pyongyang admitted in 2002 that its agents had abducted 13 Japanese, five of whom were since repatriated.
Tokyo has been seeking better information about eight others who North Korea says have died, as well as another four people it says were also kidnapped.