China has rebuffed U.S. calls for a swift U.N. Security Council response to North Korea's nuclear weapons test threat, calling the stalled six-party talks the only workable solution.

Security Council members are struggling with the question of how to respond to North Korea's nuclear threat.

As U.S. officials in Washington were warning of activity at potential North Korean nuclear test sites, U.N. Ambassador John Bolton was pushing for swift diplomatic measures that will send a strong signal to Pyongyang.

Other Security Council members, however, prefer a more cautious approach. Japan Wednesday suggested a statement urging North Korea to return to stalled six-party talks on ending its nuclear program and warning that weapons tests would jeopardize regional peace.

Pyongyang walked out of the talks 13 months ago except for a brief meeting last November. But Japan's U.N. ambassador, Kenzo Oshima, who holds the Council's presidency for October, called the six-party format Pyongyang's only option.

"I think the only way for North Korea to save itself from international isolation is to return to six-party talks," he said.

Ambassador Bolton emerged from the first of two meetings Wednesday expressing impatience with the pace of discussions. He complained that "divisions" among key Council members were delaying action.

In unusually blunt language, Bolton criticized what he called "North Korea's protectors" on the Council for stalling. He chided his Chinese counterpart, Ambassador Wang Guangya, for not being able to make any substantive contribution to the morning meeting.

"Ambassador Wang said he has no instructions today, so I'm not sure whether there's even a possibility we can have a response today," he said.

The Chinese envoy acknowledged that his country's leadership is still studying possible responses to North Korea's nuclear threat. But he rejected the U.S. call for tough diplomatic measures, and emphasized Beijing's support for the six-party format, which involves North and South Korea, Russia, China, Japan and the United States. He urged Washington to be "more creative" in trying to coax Pyongyang back to the six-party negotiating table.

"If there could be some progress made between United States and North Korea, there could be less mistrust between the two, certainly it would lead to good results. If North Korea adopts [a] more constructive approach, this will enable us to make progress, and also if the United States could be more creative in their thinking, it would help," he said.

The Chinese envoy earlier expressed doubt that the Security Council could play a role in easing nuclear tensions in the Korean peninsula until the six-party talks resume.

Several U.N. diplomats have suggested Pyongyang's test threat might be aimed at getting international attention. They note that the reclusive state has used similar devices in the past.

North Korea has long maintained it has a nuclear arsenal, but has conducted no known tests. It did, however, stage a flurry of missile tests last July. That prompted the Security Council to adopt a resolution imposing weapons-related sanctions on Pyongyang.

North Korean diplomats rejected the resolution and vowed to continue their missile program.