A Russian envoy has spoken optimistically of ending a nuclear stand-off over North Korea, as officials from both Koreas began talks on Tuesday.

Russian Deputy Foreign Minister Alexander Losyukov, who held six hours of talks on Monday with North Korean leader Kim Jong-il, said Pyongyang responded "with interest" to a Russian plan to defuse the crisis.

CRISIS CHRONOLOGY

16 Oct: N Korea acknowledges secret nuclear programme, US says 14 Nov: Oil shipments to N Korea halted 22 Dec: N Korea removes monitoring devices at Yongbyon nuclear plant 31 Dec: UN nuclear inspectors forced to leave North Korea 10 Jan: N Korea pulls out of anti-nuclear treaty 11 Jan: Pyongyang suggests it could resume ballistic missile tests

Timeline of tensions

Mr Losyukov described his three days of talks as "very useful and rather constructive".

He told Russia's Itar-Tass news agency that the North Korean leadership was currently considering Moscow's plan to end the impasse.

"They are studying it and, I believe, some elements of that plan may be used," he said. "But, of course, the dialogue must in the first place be conducted between two parties - North Korea and the United States.

"The North Korean side insists on it, and there is certain logic in this."

The United Nations Secretary-General, Kofi Annan, on Tuesday urged North Korea to reconsider its decision to pull out of the nuclear arms control treaty.

In a speech to the opening session of a UN conference on disarmament, Mr Annan said the North Korean move raises "serious concerns".

Dialogue

"I strongly urge, once again, the Democratic People's Republic of Korea to reconsider its decision," Mr Annan said.

"The only viable solution to this latest setback for disarmament and non-proliferation is through peaceful means, dialogue, and a spirit of mutual interest," he added.

South Korea also hopes to address the stand-off during four days of cabinet-level talks with North Korea in Seoul.

The talks, which are the ninth round of discussions between the two sides since an historic summit in 2000, are the highest channel of dialogue between the two Koreas.

They have focused in the past on joint projects between the two sides.

But Seoul has said it would use this week's meeting to express concerns over North Korea's move to quit the Nuclear Non-Proliferation Treaty and expel United Nations weapons monitors.

However, the BBC's correspondent in South Korea, Caroline Gluck, says that the South's influence may be limited as Pyongyang has said it is only willing to discuss the issue with Washington.

Russian plan

Washington has said that it is willing to sit down with Pyongyang, but has made no plans to do so.

Mr Losyukov: 'Useful and constructive' talks

The Russian plan reportedly envisages nuclear-free status for the Korean peninsula, security guarantees for North Korea, and a package of humanitarian and economic aid.

Pyongyang is apparently wary, though, of international mediation in the crisis.

Speaking on arrival in Seoul for the inter-Korean talks on Tuesday, North Korea's chief delegate, Kim Ryong-song, said the two sides should resist "outside pressure" and instead "join forces and unite ourselves".

Analysts believe the North may try to use the meeting to create a split between the South and its traditional ally, Washington.

A senior US envoy, the US Under-Secretary of State for arms control and international security, John Bolton, is currently in Seoul for two days of talks with government officials on the nuclear issue.

Two other sets of inter-Korean talks are also taking place this week.

One will focus on the reconnection of cross-border road and rail links. The other, involving Red Cross officials, was expected to set a new date for another round of reunions between relatives from the two Koreas who have been separated since both countries went to war half a century ago.

But those discussions are reported to have stalled due to a dispute over the size for a proposed venue for the reunions.