South Korea Monday announced aid to flood-stricken North Korea and a US envoy discussed the possible resumption of nuclear disarmament talks, amid signs of a thaw in cross-border relations.

But Seoul reiterated that Pyongyang was responsible for a deadly torpedo attack in March on a South Korean warship, an incident which sharply raised regional tensions.

And the envoy, Stephen Bosworth, stressed that Washington wants a "meaningful result" if six-nation nuclear negotiations are revived. There is "a lot of to work to do" before the talks can resume, he said.

The North, which is set to hold a key meeting of its ruling communist party, has made a series of apparent peace overtures in recent weeks after months of fiery rhetoric.

It freed a US citizen jailed for an illegal border crossing after former president Jimmy Carter visited Pyongyang, and returned the crew of a South Korean boat accused of poaching on its fishing grounds.

The North also accepted offers of flood aid and called for the restarting of a reunion programme for families separated since the 1950-1953 war on the peninsula.

The two sides will hold working-level talks Friday about a possible resumption of the programme, which has been on hold for a year, Seoul's unification ministry said.

About 80,000 elderly South Koreans are desperate for a brief meeting with family in the North but up to 4,000 of them die each year before getting the chance.

The South's Red Cross said it would send aid worth 10 billion won (8.3 million dollars), including 5,000 tons of rice, 10,000 tons of cement and three million packs of instant noodles.

Its chief Yoo Chong-Ha said the rice would go to the town of Sinuiju on the China border, which was swamped last month by an overflowing river.

He said the aid would be mainly financed by the Seoul government.

The North has announced it will hold a rare party conference this month which is expected to pave the way for an eventual leadership succession from Kim Jong-Il to his youngest son Jong-Un.

South Korean cable TV channel YTN said the meeting was delayed after Kim's health worsened following his five-day trip to China late last month.

It said the meeting would likely be held soon since Kim's health was not bad enough to merit a cancellation.

Cross-border relations have been icy since Seoul accused Pyongyang of the warship attack which killed 46 people. The North vehemently denies the charge.

The South's defence ministry Monday released a full 313-page report into the sinking.

It reaffirmed conclusions reached earlier by international investigators -- that an attack by a North Korean submarine sank the corvette in one of the peninsula's deadliest incidents for decades.

China has refused publicly to accept that its ally the North was responsible, and has instead been pushing to revive the six-party talks to ease tensions.

The United States is also involved in the forum along with the two Koreas, Japan and Russia. The North quit the talks in April last year and staged an atomic weapons test -- its second -- a month later.

The US wants a sign that the North is serious about disarmament before the nuclear dialogue restarts.

Bosworth, the US special envoy on North Korea, said after talks with South Korean officials that his country "is not interested in talking just for the sake of talking with the North Koreans.

"We want negotiations that produce a meaningful result, so we will be looking for an indication that North Korea shares that desire and determination," the envoy, who will go on to Japan and China, told reporters.