WASHINGTON -- China played an important, behind-the-scenes role in persuading North Korea to freeze its nuclear program and has since informed the United States of its efforts, Clinton administration officials and Washington-based diplomats say.


Just days before Jimmy Carter, the former U.S. president, visited Pyongyang, China's Foreign Ministry called in North Korea's ambassador to warn that his government could not depend indefinitely on Chinese support in its confrontation with the United States over its nuclear program.


The message China delivered was that it would be in Pyongyang's self-interest, for economic development and for its desire to reunify Korea, to cooperate more with international efforts to inspect its nuclear facilities, U.S. officials said. This warning is said to have been reinforced by a similar Chinese message to North Korea's ambassador at the United Nations.


"I've had Chinese officials tell me they did that and we've had other signals, too, that the Chinese were growing more and more frustrated with the North Koreans," said a senior U.S. official in an account confirmed by others in the Clinton administration. "These recent moves by China," the official said "were quite significant in terms of affecting North Korea's thinking."


Beijing's efforts to influence North Korea were timed in a way that seemed to be aimed at rewarding the U.S. administration for changes in its China policy. They came weeks after President Bill Clinton announced, on May 29, that he would extend China's trading privileges without imposing any conditions for improvements in human rights.


Neither China nor the United States has claimed there was any tit-for-tat or connection between administration help for Beijing on most-favored-nation trade benefits, on the one hand, and Chinese support for America with North Korea, on the other. But there have been suggestions of an informal, unstated link between the two issues.


"We had really, painstakingly worked with the Chinese," observed another administration official this week. "And after the MFN decision, the trend was ever clearer that the Chinese were getting fed up" with North Korea.


By directly informing the administration of its message to North Korea, China apparently was seeking to demonstrate to the White House the foreign policy benefits of avoiding further friction between Washington and Beijing.


China's willingness to weigh in with North Korea represents a significant change. Over the past year, Chinese officials have told the United States they have little or no influence over North Korea. They also have contended the United States and its allies are exaggerating the threat posed by the North Korean nuclear program.


In changing their approach toward North Korea, Chinese officials are believed to have concluded it is not in China's interest for Pyongyang to use its nuclear program to intimidate other Asian countries.


China also does not want a war on its borders and the crisis was beginning to take on military overtones. The U.S. administration had started moves to bolster its forces in South Korea and North Korea had warned the imposition of UN sanctions, sought by the United States, would be considered an act of war.