South Korea has relaxed a demand for the resumption of aid-for-disarmament talks with the rival North, saying on Friday that an apology for last year's deadly attacks is not essential to restart the process.

A senior government official, who asked not to be named, said the paramount precondition for reconvening the six-party talks was Pyongyang's sincerity about dismantling its nuclear weapons program.

The six-party talks involving the two Koreas, the United States, China, Japan and Russia stalled in 2009 when Pyongyang walked out in protest against a new round of U.N. sanctions for the North's nuclear and missile tests.

Pyongyang has said it wants to restart the talks, but Washington and Seoul have questioned its sincerity and said the isolated state was only reaching out because it wanted aid.

Relations between the two Koreas plummeted to their lowest level in years in 2010 following an attack on one of the South's warships and the shelling of a South Korean island. In November, the North also revealed major advances in its nuclear program.

Few believe the North has any intention of honoring its 2005 pledge to denuclearize, citing revelations of its uranium program which give it a second route -- alongside its plutonium program -- to make a nuclear bomb.

The two Koreas have agreed to bilateral military talks on the attacks, and Seoul has proposed separate political talks about Pyongyang's renewed pledges to denuclearize as a first step in restarting the six-party talks.

The United States had made clear that it wants to see some kind of rapprochement between the North and South before any return to the six-party forum.

The South has previously demanded the North apologize for the attacks, which killed a combined 50 people, and show sincerity on denuclearization before the broader talks could go ahead.

But the official in Seoul said an apology for the sinking of the Cheonan warship and the attack on Yeonpyeong island was now not a direct prerequisite.

The North denies it was responsible for the attack on the Cheonan warship, and said the South had provoked its artillery strike against the island. Analysts say it would have been unlikely the North would have changed its stance.

Seoul has proposed preliminary military talks on February 11 to discuss the attacks, and the rivals have also agreed to a high-level meeting, possibly at the ministerial level.

The North has not responded to the South's request for separate bilateral nuclear talks.

U.S. President Barack Obama said in his State of the Union address this week that Pyongyang must stick to its commitment to abandon atomic weapons.

The North says the uranium enrichment program is for peaceful purposes.

South Korea is pressing regional powers to take the issue to the U.N. Security Council, arguing the uranium enrichment program breaches previous agreements.