BEIJING – China yesterday rejected using sanctions to prod North Korea to return to six-nation talks on its nuclear ambitions, with a spokesman saying Beijing’s political and trade relations with its neighbor should be kept separate.

The statement from China’s foreign ministry spokesman, Liu Jianchao, came as a Bush administration official said America has asked China to redouble its efforts to lure North Korea back to negotiations.

The Washington Post reported last week that China had turned down an American request to pressure North Korea to return to nuclear disarmament talks by cutting off oil supplies.

“We stand for resolving the issue through dialogue. We are not in favor of exerting pressure or imposing sanctions,” Mr. Liu said at a regular briefing. “We believe that such measures are not necessarily effective.”

Chinese officials said a cutoff would damage the oil pipeline that links China’s northeast with North Korea because of the oil’s high paraffin content, which can clog pipelines, the Post reported.

The American appeal, disclosed by a State Department official yesterday on condition of anonymity, reflects a growing frustration over North Korea’s refusal to reopen six-nation talks for nearly a year and rhetoric from Pyongyang that administration officials consider alarming.

China, the North’s last major ally, is believed to supply the isolated communist country with as much as one-third of its food and one-quarter of its energy.

North Korea accused America yesterday of “making a fuss” by notifying allies of the communist nation’s possible preparations for a nuclear test, and maintained it would stay away from international disarmament talks. The North didn’t confirm or deny it was planning such a test.

“The United States is making a fuss saying that it was notifying the International Atomic Energy Agency, Japan, and other related countries of its own opinion that our republic may conduct an underground nuclear test in June,” the North’s main state-run Rodong Sinmun daily wrote in a commentary, ac cording to the country’s official Korean Central News Agency.

Discussions involving the two Koreas, America, China, Japan, and Russia have been stalled since last June after three inconclusive rounds. North Korea refused to participate in the fourth set of talks, originally scheduled for September 2004.

The situation became more urgent last week when American officials said spy satellites showed possible preparations for North Korea’s first nuclear weapons test. Those included digging and refilling a large hole at a suspected test site.

Asked if China believed Pyongyang was preparing for a test, the Foreign Ministry spokesman, Mr. Liu, would not answer. He said he did not have any “confirmation of relevant reports.”

Tensions increased further over the weekend, when North Korea called President Bush a “hooligan” after Mr. Bush characterized North Korean leader Kim Jong Il as a “tyrant.”

Mr. Liu indirectly criticized Mr. Bush’s remarks, saying that “any party of the six-party talks should take measures and words and actions that are favorable to the resumption of the talks, and should not say or do anything not conducive to continuing the six-party talks.”

The North appeared to soften its position on returning to talks, saying Saturday it wasn’t demanding direct meetings with Washington outside the six nation negotiations.

On Monday, a State Department spokesman said American officials had previously spoken directly with North Korean officials within the context of the six-party talks, and that it was willing to do so again if Pyongyang returns to the table.

Mr. Liu said Beijing would be pleased with any contacts between the North and America.