Lack of progress in nuclear talks between U.S. and North Korea

The U.S. envoy pledged to keep at nuclear talks with North Korea, meeting again with the North's delegate as negotiations stretched into the longest round.

All six chief delegates met later Friday and agreed to continue the talks Saturday, China's official Xinhua News Agency reported.

U.S. Assistant Secretary of State Christopher Hill held a one-on-one meeting Friday morning with North Korean Vice Foreign Minister Kim Kye Gwan at the state guesthouse where the talks are taking place, Xinhua said. No results of the meeting - their fourth direct talks this week - were immediately known.

No deadline has been set for the nuclear talks in the Chinese capital to wrap up, unlike other sessions that lasted about three days. The six-nation talks that began Tuesday are the fourth round in which China, Japan, Russia, South Korea and the United States have come together to press North Korea to give up its nuclear ambitions.

"We'll just keep at it just as long as it's useful to keep at it. I've got plenty of patience," Hill said Friday before his meeting with the North Koreans.

He said the meeting was to focus on discussions of denuclearization of the Korean Peninsula - the buzzword of the negotiations, whose definition remains a point of contention, the AP reports.