U.S. official hails close cooperation on North Korea

"I have rarely seen better coordination between China and the United States in particular," Campbell told reporters on Wednesday in Beijing, where he has met Chinese officials.

"There is a virtually unprecedented acceptance of basic goals and ambitions associated with the six-party talks and negotiations with North Korea."

He was speaking a day after South Korea's Yonhap news agency reported that the North was preparing to fire a fresh barrage of missiles, in a bid to boost its bargaining position ahead of expected nuclear talks.

Campbell said North Korea's neighbours all agreed the six-party disarmament talks remain key to resolving the issue and that any bilateral talks could only take place within the framework of the multi-lateral talks.

"We are now reviewing steps in the near future," he said, adding that the U.S. was also in close consultations with Japan and South Korea.

"I think we will have more to say about this shortly."

North Korea test-fired short-range missiles on Monday, South Korean media reported, just as the reclusive state had been signalling it might return to nuclear talks.

(Reporting by Chris Buckley; Editing by Lucy Hornby and Sanjeev Miglani)