President Bush, with Chinese Premier Wen Jiabao at his side in the Oval Office, delivered a firm warning yesterday to the Taiwanese government over its aspirations for independence, telling the island's leaders not to pursue a referendum that has angered mainland China.

Bush raised no objection when Wen said Bush had expressed his "opposition to Taiwan independence" -- a break from the policy of ambiguity the United States has had on the subject. Bush, in his remarks with Wen, made no specific criticism of China but declared that "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."

Taiwanese President Chen Shui-bian swiftly rebuffed Bush, saying the referendum would proceed but adding that Taiwan was not planning to declare independence and would not try to change the "status quo" between it and China, a spokesman said early today in Taipei.

Administration officials asserted after Bush's statement that there was no change in China policy, but the remarks in the Oval Office were a significant change in emphasis for the administration. Two years ago, it took an aggressive position toward China, saying the United States would "do whatever it takes" to defend Taiwan.

Bush's admonishment of Taiwan yesterday came in response to a reporter's question about the referendum, which would not directly address independence but would call on China to withdraw ballistic missiles aimed at the island.

Bush's actions provoked a furious reaction from conservative critics of Beijing, who had strongly supported Bush's invasion of Iraq and his vow to further a "world democratic movement." A trio of influential conservative commentators yesterday accused the Bush administration in a statement of rewarding "Beijing's bullying" while saying "not a word" about China's missile buildup and threats of war against Taiwan.

"The president's statement today is a mistake," wrote William Kristol, Robert Kagan and Gary Schmitt. "Appeasement of a dictatorship simply invites further attempts at intimidation."

The sentiment was widespread among some conservatives. John Tkacik, a China expert at the Heritage Foundation, said the president's comments showed "he's lost his bearings" on the Taiwan issue. "It just boggles the mind," he said. "I'm just appalled. Clinton never would have gone this far."

Tkacik noted that Bush has recently promoted the cause of democracy in the Middle East, and Taiwan is a thriving democracy. "It is incongruous for an American president who just gave a speech on democracy in the Middle East to tell the people of Taiwan who they can elect," he said.

In a White House briefing for reporters provided on the condition that the officials not be identified, a senior administration official said Bush's statements might be perceived as a tilt toward China. But he suggested that the administration decided that was a risk worth taking in light of actions by Chen.

"I'll tell you there was some concern about that," he said. But "the situation is constantly evolving on Taiwan and there are constantly new statements being made, and there was felt a need to make it clear that Taiwan must be careful."

The official said Bush was more assertive with Wen in their 40-minute private meeting, calling the president "very, very forceful" in warning China not to use force against Taiwan. But the officials declined repeated requests to say whether Bush had opposed Taiwanese independence, as Wen asserted. Until now, the United States has used the more neutral statement that it "does not support" independence.

The shifting U.S. emphasis on Taiwan has come after actions by Chen that the administration considers provocative, particularly the plans to hold the referendum in the spring to protest the missiles.

Although he did not criticize publicly China's actions toward Taiwan, Bush yesterday said the administration remains committed to the "one China" policy and the Taiwan Relations Act, which says military action by China against Taiwan would be a "grave threat" to security.

James R. Lilley of the American Enterprise Institute said Bush's invoking of the Taiwan Relations Act signaled that "we are not going to betray Taiwan." But he also said Bush put himself in a difficult position by opposing the referendum because there was little he could do if Chen ignores the U.S. warning. "We'll say, 'You've hurt our feelings,' " said Lilley, the ambassador to China under President George H.W. Bush.

The White House left ambiguous the consequences for Taipei of holding the referendum. Asked about the use of sanctions, press secretary Scott McClellan said: "I'm not going to rule it in or rule out." The spokesman said Bush told Wen that the United States opposes Taiwan's pursuing any "referenda and constitutional reform that would change the status quo."

The warning by Bush came after Chen's government was unmoved by similar words delivered in a briefing by an unnamed senior administration official on Monday.

Wen, whose government Bush embraced as "partners in diplomacy," appeared pleased with Bush's remarks. He thanked Bush for opposing Chen's "attempt to resort to referendum of various kinds as an excuse to pursue Taiwan independence."

Bush appeared to receive little tangible in exchange for his gesture. The two leaders, who also lunched together, discussed the two countries' trade imbalance, the way the value of Chinese currency is set, religious freedom and talks to defuse the nuclear crisis with North Korea. But the administration announced no concrete gains.

On North Korea, a senior official said, Bush and Wen "felt there was a developing consensus on this issue but that we had not yet reached the point" where another round of six-nation talks could be convened to resolve the crisis. Officials had hoped to hold the talks this month. Another official involved in North Korean issues said the Chinese did not appear pleased with a draft statement guiding the talks that was written last week by the United States, Japan and South Korea.

Bush rejected a North Korean suggestion that it would freeze its nuclear program in exchange for fuel aid and removal from the U.S. list of terrorism sponsors. "The goal is to dismantle a nuclear weapons program in a verifiable and irreversible way," he said.

Schmitt, director of the Project for the New American Century, said the public exchange between the two leaders made it appear that "Taiwan is the provoker." Schmitt said the administration was making a doomed effort "to try to freeze the status quo," back before the Chinese military buildup and Chen's push on referendums. Those escalations occurred while the United States was preoccupied with Iraq.

State Department spokesman Richard Boucher said Bush's opposition to a referendum in Taiwan is consistent with his overall support for democracy.

"I think it's quite clear that our support for democracy doesn't mean that sponsoring referendums on any subject in particular around the world at any given moment is necessarily a wise course or one that might lead to stability and benefits to the people who are being invited to vote," he said.

Visiting Chinese Premier Wen Jiabao and President Bush greet onlookers at the White House.President Bush welcomes Chinese Premier Wen Jiabao to the White House during a ceremony on the South Lawn.