China says the United States has inflamed the conflict on the Korean Peninsula and must carry the burden of ending it in the wake of North Korea's fifth nuclear test.

The detection Friday of a nuclear warhead being detonated in North Korea placed new international pressure on China, Pyongyang's economic lifeline and the closest thing it has to a political ally.

U.S. Defense Secretary Ash Carter said China had an "important responsibility" in North Korea. But Chinese Foreign Ministry spokeswoman Hua Chunying said Monday that Carter was "being too modest."

Citing a Chinese saying that "whoever started the trouble should end it," Hua said the U.S. "should take on its due responsibility."