Pyongyang also reaffirmed its commitment to rejoining the Non-Proliferation Treaty and returning unconditionally to six-nation talks on its nuclear program next month, he told journalists in Tokyo.

North Korea suspended its membership in the nuclear NPT in 1993 and placed limitations on International Atomic Energy Agency (IAEA) inspections. It withdrew from the treaty altogether in December 2002 and kicked out inspectors.

Richardson, now governor of the US state of New Mexico, came to Tokyo after a four-day tour of North Korea where he met top officials including Kim Yong-Nam, the Stalinist country's number two, for their third meeting.

"They ... indicated they would at an appropriate time invite IAEA officials, including (director) Mohamed ElBaradei, to North Korea," he said.

The officials "reaffirmed their commitment to rejoining the Non-Proliferation Treaty, also adhering to IAEA safeguards," said the former energy secretary and UN ambassador under former US president Bill Clinton.

He said North Korean officials agreed to return to six-party talks in November "unconditionally".

The two Koreas, China, Japan, Russia, and the United States resumed the talks on scrapping North Korea's nuclear arsenal in Beijing in September. A next round is expected in the Chinese capital in November.

At the last round of talks, North Korea agreed to a statement of principles under which it would give up its atomic weapons in return for energy and security guarantees.

But the secretive state later said it would not dismantle its nuclear arsenal until the United States delivers light-water reactors to allow it to generate power, leaving the prospect of prolonged multilateral wrangling.

Richardson said North Korean officials "showed some flexibility" in their attempt to receive the light-water reactors.

"They are prepared for oversight of the light water reactors by the United States, the IAEA or other six-party countries, in terms of co-managing, in terms of having the Untied States participate in the fuel-cycle at the front end and the back end," he said.

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