Beijing on Thursday denounced remarks of US Senator John McCain as "irresponsible" after he said China's Diaoyu Islands are "Japanese territory".
The Republican lawmaker is "muddying the waters" at a time when tensions over the islands standoff between China and Japan are running high, and he is making trouble for Washington on the issue, observers said.
McCain said in Tokyo on Wednesday that "the Chinese are violating fundamental rights that Japan has" to the islands.
Nations feeling increasingly threatened by China's maritime presence "need to act in closer coordination with each other", the said.
Foreign Ministry spokesman Hong Lei rebutted such comments. "The Diaoyu Islands have been China's territory since ancient times, and any individual's attempt to deny the facts will be in vain," he told China Daily on Thursday.
"We urge the US lawmaker to stop making irresponsible remarks and avoid further complicating related issues and the regional situation."
Ruan Zongze, vice-president of the China Institute of International Studies, said McCain is "not entitled" to speak on behalf of the US government and his remarks will embarrass Washington.
Kyodo commented that McCain's remarks deviate from the official US stance that the United States does not take a position on the sovereignty of the islands.
"Washington previously has clarified its position in this regard, and seems to have no plan to change its vagueness on it," Ruan said.