BEIJING — China appealed for "coolheadedness" on all sides in the North Korean nuclear crisis today, amid signs that an exasperated Beijing is willing to get tougher with its traditional ally.

Secretary of State Condoleezza Rice appealed to North Korea to return to stalled international talks over its nuclear program without condition. Concluding urgent talks in Asia in response to the North's Oct. 9 nuclear test, Rice played down differences among the U.S., China and South Korea over the strength and tone of world response to Pyongyang.

She told reporters China has new resolve against the North that shows it has reevaluated its relationship with Pyongyang. Last week's United Nations Security Council vote to impose sanctions on Pyongyang proves the point, Rice said.

"In this entire 30-year history of the North Korean nuclear program this is the first time that the international system has been able to actually impose a cost on North Korea for its nuclear behavior," Rice said. "It's able to impose that cost because China has been brought into the process in a way that China never was before."

The U.S.-backed sanctions were watered down partly at China's request, but China's vote in favor of punishment still represents a shift for Beijing.

"We hope all relevant parties will maintain coolheadedness, adopt a prudent and a responsible approach and adhere to peaceful dialogue," Foreign Minister Li Zhaoxing said earlier, following a meeting with Rice.

The underground test confirmed the North's claim that it has nuclear weapons capability and raised fears of potential war or an arms race in Asia.

At a brief joint appearance with Li, Rice said both President Bush and Chinese President Hu Jintao want a peaceful diplomatic solution. She did not mention the U.S. military commitment to defend allies Japan and South Korea from an attack by the North, a centerpiece of her remarks in those nations earlier this week.

Rice's conciliatory tone appeared to be aimed at keeping Beijing's cooperation.

Li assured Rice that Beijing would carry out its obligations, although he avoided the word sanctions and gave no specifics.

"China has an excellent track record in playing a constructive role in the international community and in honoring all of our commitments," he said.

Chinese moves to close off North Korean access to the global financial system appear to bear out Li's pledge.

Chinese banks have stopped financial transfers to North Korea under government orders as part of the sanctions, bank employees said today.

China is North Korea's main trading partner and aid donor, and has long been reluctant to use economic pressure against the North for fear the government of Kim Jong Il might collapse.