The Chinese government has downplayed remarks by a senior general suggesting that China might use nuclear weapons if the US attacked it over Taiwan.
Major General Zhu Chenghu was only expressing "personal views", Beijing officials said.
A foreign ministry spokesman said Beijing was committed to its policy of peaceful re-unification with Taiwan.
A US state department spokesman has described Gen Zhu's remarks as "unfortunate" and "irresponsible".
China regards Taiwan as a renegade province.
The Chinese general, who is not directly involved in China's military strategy, made his remarks to foreign reporters on Friday.
"If the Americans draw their missiles and position-guided ammunition onto the target zone on China's territory, I think we will have to respond with nuclear weapons," Maj Gen Zhu told an official briefing for foreign reporters.
The general said his comments were "my assessment, not the policy of the government".
He said he was confident the US and China would not go to war.
The US is currently Taiwan's biggest arms supplier and has indicated it would defend the island in the event of a Chinese invasion.
Gen Zhu's remarks come at a time when many US politicians are already concerned about China's military build-up.
State department spokesman Sean McCormack said he hoped they did not reflect Chinese official policy.
On Saturday, the Chinese foreign ministry said: "We will firmly abide by the principles of peaceful re-unification and one country two systems and we will express the deepest sincerity and exert the greatest efforts to realise peaceful reunification.
The US is Taiwan's biggest arms supplier
"We will never tolerate the 'Taiwan independence'," the spokesman said.
He said China appreciated the US government's repeated commitments to the one-China policy.
"We hope the United States will fulfil its commitments with concrete actions and join efforts with China to maintain the peace and stability across the Taiwan Strait," he said.