In the wake of U.S. scientists' conclusion that Libya recently obtained uranium that was enriched in North Korea, the New York Times reports that the Bush Administration has increased its pressure on China to force North Korea to give up its nuclear weapons program.

President Bush's message was carried directly to Premier Hu Jin Tao himself by two officials of the National Security Council. China asked the Bush Administration to refrain from making provocative public statements about North Korea's alleged proliferation while its officials make high-level inquiries in Pyongyang. In his inaugural and state-of-the-union addresses, President Bush's comments about North Korea were restained, even mild, compared with his comments about Iran and Syria.

The Times article also suggested that confirmation of the uranium transfers to Libya has fueled the administration's impatience with the lack of progress in six-nation talks to dismantle North Korea's nuclear program. A breakdown of the talks raises the possibility that President Bush could side with those who support regime change, by isolating North Korea to bring down what is left of its economy, or by encouraging internal dissent. According to the Times article, the new revelations about North Korean uranium found in Libyan possession have "energized" those who favor such measures if talks fail to convene and bear fruit in the near future.

American and Asian intelligence officials say it is unclear whether North Korea knew that Libya was the ultimate destination for the chemical, called uranium hexafluoride. One senior official with access to the intelligence data said it was possible that the North Koreans only knew that it was transferring the fuel to members of Dr. Khan's network. "We don't know how much they produced, or if it was shipped elsewhere," the official said. "It's one of the questions we have to get answered."

The Times article quotes administration officials as saying that a profile of the isotopes in plutonium found on the Libyan containers matched samples known to come from Yongbyon, North Korea. The officials added that since Pakistan is not believed to have a source of plutonium other than North Korea, the presence of plutonium suggests a North Korean origin.

There is a history of extensive collaboration between the North Korean and Pakistani nuclear weapons programs--including joint efforts at design, production, and testing--presumably ending with the recent exposure and dismantling of the Pakistan-based A.Q. Khan network. Revelations from the Khan network, in turn, led to a Libyan agreement to give up its nuclear weapons program.

China, which supplies most of North Korea's fuel, has recently demonstrated its ability to pressure North Korea on matters that are important to China.