The chief nuclear envoys for North and South Korea met in Beijing on Wednesday but failed to agree on a possible revival of the stalled six-nation talks on ending the North's nuclear weapons programs.

The three-hour meeting at a private members' club in the center of the Chinese capital was the second round of talks in two months between the South's Wi Sung-Lac and his North Korean counterpart Ri Yong-Ho.

According to Yonhap news agency, the diplomats ended the talks without any concrete results but both said their discussions were "useful."

"We discussed the nuclear problem in general, and a meeting such as this is part of the efforts to restart the six-party talks," Wi Sung-Lac told reporters after the meeting. "We will keep putting in these efforts."

The South Korean diplomat insisted that Pyongyang should accept "pre-steps" demanded by Seoul and Washington before the resumption of the six-party talks. These preconditions stipulate that North Korea must halt all nuclear activities, including its uranium enrichment program, and allow U.N. inspectors to monitor the suspension before the six-party talks reopen.

Ri Yong-Ho spoke on Wednesday of a "constructive" dialogue with his South Korean counterpart but repeated calls for an "unconditional" resumption of the six-party negotiations.

The six-party talks on Pyongyang's nuclear ambitions involving the two Koreas, China, the United States, Russia and Japan began in 2003 and came to a halt in April 2009 when North Korea walked out of negotiations to protest the United Nations' condemnation of its missile test.

The negotiating process was resumed in July when Wi Sung-Lac and Ri Yong-Ho met in Bali, Indonesia, for the first time in two and a half years.