He said North Korea, which has sometimes made contradictory statements about its intentions, indicated it was willing to re-join the non-proliferation treaty (NPT) and adhere to international standards for its nuclear program.

Pyongyang is due to take part in resumed six-nation nuclear talks in Beijing in November, and Richardson said it was "sending signals of wanting to engage" -- even on the contentious issue of nuclear power reactors.

"My sense is that they want more dialogue with the United States," said Richardson, a former US energy secretary and US ambassador to the United Nations who has now held three meetings with top North Korean officials.

North Korea suspended its membership of the 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, who met Pyongyang's number two official Kim Yong-Nam, said North Korea was ready to return "unconditionally" to the talks and that IAEA officials would be invited for a visit.

"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 (and) also adhering to IAEA safeguards," he said.

At talks last month, North Korea pledged to give up its nuclear weapons in exchange for promises of aid and security, the first major breakthrough in more than two years of deadlock over Pyongyang's atomic ambitions.

In return, the United States said it would respect the North's sovereignty and would not attack, a fear Pyongyang had repeatedly said was a main reason for insisting on developing an atomic bomb program.

But after the agreement was announced, North Korea, which is badly short of electricity, immediately said it would insist on having light-water nuclear reactors for civilian energy purposes before giving up its weapons.

Richardson said North Korean officials "showed some flexibility" in their attempt to gain light-water reactors, an issue he said was not likely to be a "deal breaker."

"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.

But Richardson said negotiators would have to establish a "very strong regime of verification" given Pyongyang's record of broken promises to international bodies.

The standoff with North Korea erupted in October 2002 when the United States said North Korea was running a secret uranium enrichment program in violation of an earlier deal that had allowed construction to start on two reactors.

Although he did not receive specific responses to his questions on nuclear weapons, the US politician believes the North's claim already to have atomic bombs was true.

"The sense of the response I got was that they have a small number on the lower end of one to five," Richardson said.

Meanwhile, North Korea also promised Richardson to allow 30 international workers of the World Food Program to stay in the Stalinist state, as well as staff from some 30 non-government organizations to provide humanitarian aid. Pyongyang has previously threatened to kick them out.