Beijing, China ? The U.S. and Chinese governments announced Tuesday that North Korea agreed to rejoin six-nation nuclear disarmament talks, a surprise diplomatic breakthrough that comes only three weeks after the communist regime conducted its first known atomic test.

The agreement was struck in a day of unpublicized discussions between the senior envoys from the United States, China and North Korea at a government guesthouse in Beijing. The U.S. negotiator, Assistant Secretary of State Christopher Hill, said the six-nation negotiations could resume as early as November or December.

“We took a step today toward getting this process back on track. This process has suffered a lot in recent weeks by the actions the DPRK has made,” Hill told reporters afterward. DPRK stands for Democratic People’s Republic of Korea, the North’s official name.

The agreement is one of the first signs of easing tensions since North Korea conducted the underground detonation on Oct. 9, defying warnings from both the United States and Japan and its staunchest ally, China.

It also marks a diplomatic victory for China and the United States, which worked closely together in the wake of the test, but especially for Beijing. Though stung by Pyongyang’s test, China had counseled against punishing North Korea too harshly, weakening a U.N. resolution sanctioning Pyongyang, and suggested leaving a path for diplomacy.

In a possible sign of Beijing’s growing impatience with Pyongyang, Chinese exports of diesel and heating oil to North Korea dropped substantially in September from a year ago, though exports of gasoline, liquefied petroleum gas, kerosene and jet fuel rose, according to Chinese customs data. China provides most of the North’s oil.

President Bush hailed the agreement and credited China with helping to bring it about. “I am pleased and I want to thank the Chinese,” the president told reporters in the Oval Office.

But he said the agreement would not halt the U.S. efforts to enforce the U.N. Security Council resolution that imposed sanctions on trade in military materials and luxury goods in response to the North’s atomic test.

State Department spokesman Tom Casey said the U.S. would enter the new round of talks insisting they start with a September 2005 agreement forged among the six nations, in which Pyongyang pledged to scrap its nuclear programs in return for aid and security assurances.

Talks between the U.S. and North Korea over its nuclear programs have had a tortuous history, beginning in a 1990s round that led to a freeze that the Bush administration claims Pyongyang violated.

Starting first as a three-way parlay with Beijing, the current round of negotiations then added Japan, Russia and South Korea, before holding three on-again, off-again sessions. The negotiations stalled after the U.S. imposed financial sanctions over alleged counterfeiting and money laundering activities by Pyongyang and North Korea withdrew in November 2005.

Both the U.S. and North Korea showed flexibility at Tuesday’s meeting, Hill said, with Washington agreeing to discuss the financial sanctions. The U.S. previously had said the issue was unrelated to talks on Pyongyang’s nuclear program.

Pyongyang did not make the lifting of the financial sanctions a condition for resuming the talks, Hill said.