China and the U.S. have the two most powerful economies and are two of the largest energy users. They agreed to hold high-level talks on climate change and to ease business investment cooperation.

Kerry also raised the possibility of scaling back America's military presence in the Asia-Pacific region once the Korean nuclear crisis is resolved. Beijing has been disgruntled about U.S. missile defense systems in China's backyard.

"Obviously, if the threat disappears," meaning a nuclear-free North Korea, "the same imperative does not exist at that point in time for us to have that kind of robust, forward-leaning posture of defense," Kerry said. "And it is our hope in the short run that we can address that."

Western experts predict that China will move slowly and cautiously, if at all, toward becoming a more reliable U.S. ally. China remains deeply skeptical of President Barack Obama's policy shift to Asia, which Beijing views as U.S. attempts to contain its economic might.

It's also unlikely that China will sever its long ties with North Korea. The Chinese dramatically have boosted trade with their neighbors and maintain close military relations some six decades after they fought side by side in the Korean War. They provide North Korea with most of its fuel and much of its food aid.

China has a history of quickly reversing course after talking tougher with North Korea. In late 2010, as American officials were praising Beijing for constructive efforts after the North shelled a South Korean island, a