The North told visiting Russian envoy Alexei Borodavkin that it was willing to return to the six-party talks "without any precondition", Pyongyang's state media quoted a foreign ministry spokesman as saying.

In talks with the Russian deputy foreign minister, the North also said it would not oppose discussions at the six-party forum on its disputed uranium enrichment programme; Korea Central News Agency quoted the spokesman as saying.

Russia called for "constructive" measures by Pyongyang, such as a moratorium on nuclear tests and ballistic missile launches, access for international experts to uranium enrichment facilities, and six-party discussion of the uranium programme, KCNA said.

The North said it was a peaceful energy project but experts said the facility could hand Pyongyang a second route to making atomic bombs on top of its existing plutonium stockpile.

Professor Yang Moo-Jin of the University of North Korean Studies said Pyongyang was acknowledging international concern over the uranium enrichment programme even while it insists on its peaceful intention.

"The statement adds momentum to diplomatic efforts to resume the six-party talks," Yang told AFP.

Borodavkin, Kremlin's chief envoy for the six-party forum, visited Pyongyang between Friday and Monday, meeting Foreign Minister Pak Ui-Chun and other North Korean officials.

The Russian envoy also offered closer economic ties as a means of easing regional tension, proposing projects to build railways, gas pipelines and electricity networks connecting Russia and the two Koreas.

The North "expressed support" and would "positively examine" the offers, KCNA said.

The trip came as South Korea deepens efforts to secure international condemnation of the North's nuclear programme after a year of tension on the peninsula.

Cross-border tension flared after Pyongyang's alleged sinking of a Seoul warship in March 2010, which killed 46 sailors, and escalated when the North shelled a border island in November, leaving four South Koreans dead.

Cho Hyun-Dong, the South's deputy nuclear envoy, left for Russia Tuesday to meet Borodavkin.

Russia, along with Washington and Tokyo, has backed Seoul's call for the UN Security Council to debate Pyongyang's uranium programme.

But China, the North's strong ally, said the uranium program should be handled at the six-party talks.

Beijing also blocked an attempt last month by Seoul and Washington to publish a UN report criticising the North's uranium program.

"Pyongyang obviously needs more help from Russia, a Cold War era ally, to revive the six-party talks and avoid another UN condemnation," said Cheong Seong-Chang of the Sejong Institute think tank.

"The latest remark is the North's gesture aimed to urge Russia to play a bigger role to create a breakthrough in the long-stalled negotiation," he said.

Six-party talks grouping the two Koreas, Japan, Russia, the United States and China have been deadlocked since Pyongyang walked out in April 2009 in protest at UN condemnation of an apparent missile test.

The hard line state staged its second nuclear test the following month, sparking tougher UN sanctions.