WASHINGTON — Sending a blunt warning to a longtime Asian partner, President Bush cautioned Taiwan's leadership Tuesday against "comments and actions" aimed at independence, telling visiting Chinese Premier Wen Jiabao that the United States opposes such steps.

Bush also put Wen on notice that any military action against Taiwan by China would invite a forceful response from the United States, reiterating an earlier pledge to defend the island republic from potential mainland aggression.

The comments came amid mounting U.S. worries over escalating tensions between Taiwan and China. Taiwanese President Chen Shui-bian has called for a referendum next March calling for China to withdraw all missiles aimed at Taiwan and to renounce the use of force against the island. Beijing, which has deployed 500 offensive missiles within striking distance of Taipei, views the referendum as a move toward independence.

"We oppose any unilateral decision, by either China or Taiwan, to change the status quo," Bush told reporters during a brief Oval Office photo session with Wen. "And the comments and actions made by the leader of Taiwan indicate that he may be willing to make decisions unilaterally to change the status quo, which we oppose."

Wen, the first of a new generation of Chinese leaders to visit the White House, responded that China would seek to settle its differences with Taipei peacefully, "so long as there is a glimmer of hope" for doing so.

He also accused Chen of trying "to split Taiwan away from China."

Beijing regards Taiwan as a breakaway province, owing to its 1949 split from the mainland in the midst of civil war when communists took control of China. Since then, Taiwan has functioned as a sovereign entity.

"The Chinese government respects the desire of people in Taiwan for democracy," said Wen, who, as premier, is the No. 2 official in China's one-party communist government. But he accused Chen of "only using democracy as an excuse and attempt to resort to (a) defensive referendum to split Taiwan away from China."

Bush's comments, following a 40-minute Oval Office meeting with Wen, appeared to tilt U.S. policy slightly toward Beijing on a delicate subject that has for decades been a major irritant in Sino-American relations.

A senior aide to Bush later told reporters the shift in emphasis was spawned by growing fears of a potential conflict across the 90-mile strait dividing Taiwan from mainland China.

"Were either side moving unilaterally to change the status quo, we oppose that, we don't want to see it, we think it's dangerous," said the official, who was authorized to brief reporters on the condition of anonymity. "We think anything that looks like a unilateral move towards independence on the part of Taiwan can start down a dangerous road."