Top nuclear envoys from North and South Korea will hold bilateral talks on Wednesday in Beijing, aimed at discouraging the North from going ahead with its nuclear weapons development programme, South Korea's Yonhap news agency said on Sunday.

"The South and the North agreed to set a date for the nuclear talks on September 21," Yonhap quoted a senior Seoul government official as saying. "The exact time and frequency will be discussed there (in Beijing)."

South Korean media have reported Wi Sung-lac, South Korea's chief nuclear negotiator, and his North Korean counterpart Ri Yong-ho were already in the Chinese capital to prepare for what would be their second meeting in two months.

Comments from Seoul officials to confirm the news report were not immediately available.

Under pressure from their main allies in Washington and Beijing to iron out their differences, the rival Koreas moved a step forward to restart six-party aid-for-denuclearisation talks, which involve the United States, China, Japan and Russia, when Wi met Ri in Bali, Indonesia, in late July.

A week after that meeting, which was described as "constructive", a top North Korean diplomat visited New York for talks with U.S. special envoy for North Korea, Stephen Bosworth.

The North, still technically at war with the South after the 1950-53 Korean War ended with an armistice rather than a peace treaty, has said it is willing to return to the six-party talks without preconditions.

Seoul and Washington demand that Pyongyang must first halt its uranium enrichment programme and allow the return of international nuclear inspectors.

North Korea walked out of the six-party talks more than two years ago after the United Nations imposed a new round of sanctions on it for conducting nuclear and missile tests.

Last year, relations between the two Koreas were damaged and regional tensions heightened by the killing of 50 South Koreans in two separate attacks on the peninsula.