Mr Richardson was allowed to tour Yongbyon nuclear plant

Bill Richardson said he was "very pleased" with North Korea's willingness to make progress in six-nation talks.

Pyongyang has already pledged to abandon its nuclear weapons in an earlier round of the talks.

Mr Richardson, former US ambassador at the UN, said North Korea now wanted to focus on a civilian nuclear programme.

"Their view is that what needs to be addressed is the light water reactor," he said.

North Korea has said it will renounce its nuclear weapons in exchange for aid and security guarantees and foreign help in building a civilian nuclear programme.

Mr Richardson said Pyongyang officials had indicated they may eventually allow US and other monitors into the country to ensure none of the spent fuel from a civilian reactor is diverted to weapons.

'Show of transparency'

Mr Richardson, the governor of the US state of New Mexico, spent several days meeting North Korean officials and touring their nuclear facilities last week.

He later told the South Korean foreign minister that the North had indicated it was willing to comply with international non-proliferation treaties and to allow UN monitoring of its nuclear programme.

"I was impressed with their tone, and their commitment to principles," he told reporters in the South Korean capital, Seoul.

Mr Richardson said he had been allowed to tour a nuclear facility in Yongbyon, in an apparent "show of transparency" that "bodes well for six-party talks".

The next round of talks - involving the two Koreas, China, Japan, the US and Russia - will be held in the first week of November, he said.

"My view is that we should not expect an agreement in the next round," he said. "There will be measurable progress that might lead to a future agreement."

Food aid

The nuclear dispute with Pyongyang began in late 2002, when the US accused North Korea of having a uranium-based nuclear arms programme, in violation of international agreements.

Separately, Mr Richardson said North Korea had told him UN food aid workers will be allowed to remain in the country, reversing an earlier threat to kick them out.

In recent years, the UN and other international agencies have been feeding up to six million of the poorest and most vulnerable North Koreans.

Mr Richardson said a new agreement could enable the UN's World Food Programme workers to stay on "under a renewed definition of what development aid is".