Olli Heinonen, deputy director general of the International Atomic Energy Agency (IAEA), said at the airport he was upbeat about the negotiations on North Korea's only operating reactor in Yongbyon, but added he did not know whether IAEA experts would visit the facilities, Japan's Kyodo Tsusin agency said.
Depending on the results of the visit, six negotiators on North Korea's nuclear program - the United States, Japan, China, Russia, North and South Korea - will decide on further negotiations. The talks could be resumed in early July, and foreign ministers of the six countries might meet in August in Manila, the Philippines, during the Asia-Pacific economic forum (ASEAN).
North Korea invited the IAEA delegation immediately after it became clear that its $25 million frozen in China's Macao bank over U.S. money laundering suspicions had been virtually transferred home despite numerous delays.
U.S. negotiator Christopher Hill paid a surprise visit to Pyongyang last week and said North Korea was prepared to suspend or even deactivate its reactor.
The reclusive Communist state severed contacts with UN weapons inspectors during the first nuclear crisis in 1994 but later agreed with the U.S. on the construction of light water reactors on its territory. The plans were thwarted in 2002 when North Korea expelled international inspectors from the country.
In February, North Korea agreed to suspend its reactor in exchange for aid, and the IAEA director general, Mohamed ElBaradei, visited the country in March.
