North Korea called on Monday for an early resumption of six-party nuclear talks "without preconditions" but South Korea said its neighbour must first suspend its atomic activities.
Pyongyang and Washington have agreed to hold further dialogue, a spokesman for the North's foreign ministry said, after last week's visit to New York by a senior official from the communist state.
The North "remains unchanged in its stand to resume the six-party talks without preconditions at an early date" and comprehensively implement a 2005 denuclearisation deal, the spokesman told the North's official news agency.
Pyongyang walked out of the negotiations in April 2009, a month before it carried out its second atomic weapons test.
But last month the chief nuclear negotiators from the two Koreas held surprise talks in Bali on the sidelines of a regional security conference.
And last Thursday and Friday the North's first vice foreign minister, Kim Kye-Gwan, met Stephen Bosworth, the US special envoy on North Korea, for talks in New York.
It was the first high-level contact since Bosworth visited Pyongyang in December 2009.
The New York talks were "sincere and constructive", the North's spokesman said.
"Both sides recognised that the improvement of the bilateral relations and the peaceful negotiated settlement of the denuclearisation of the Korean peninsula conform with the interests of the two sides and agreed to further dialogue," the spokesman said.
Under a six-party deal in September 2005 the North agreed in principle to scrap its atomic weapons programme in return for economic aid and major security and diplomatic benefits.
But the agreement eventually broke down, amid accusations of bad faith by both sides.
Last November the North revealed an apparently operational uranium enrichment plant, potentially giving it a second way to build atomic weapons in addition to its plutonium-based activities.
South Korea's chief nuclear negotiator Wi Sung-Lac said the North must take concrete action on denuclearisation before the six-party talks can resume.
"We cannot go to six-party talks when (the North's) nuclear programmes are up and running," he told reporters Monday, adding it was "too ambitious" to expect the forum to reopen this autumn.
Wi said his Bali meeting with his counterpart from the North was "quite cordial" but there was no kind of breakthrough or tangible outcome.
The enriched uranium programme was a clear violation of UN Security Council resolutions, Wi said, and "has to be addressed and stopped".
The United States said Friday the "path is open" to better relations if the North shows a firm commitment to disarmament efforts.
Cross-border ties have been icy since the South accused the North of sinking a warship with a torpedo and killing 46 sailors in March last year.
The North denied the charge but killed four South Koreans with an artillery bombardment of a border island last November.
The cross-border animosity has complicated efforts to restart the six-nation forum grouping the two Koreas, China, the United States, Russia and Japan.
In recent months, the North's state media have resumed their harsh criticism of the South's conservative leaders. Its military has threatened attacks in response to perceived provocations.
The reason for the apparent switch to diplomacy was unclear, but Pyongyang's regime is seeking international food aid.