China lashed out yesterday at the Bush administration's policies on Taiwan and Hong Kong, declaring it is "gravely concerned" that the issues will undermine progress on U.S.-China relations.

The tough statement, made at a rare news conference called by the Chinese Embassy spokesman in Washington, came just days after national security adviser Condoleezza Rice toured the region and met with top Chinese officials. During the trip, Rice rebuffed demands from China that the United States curb arms sales to Taiwan, but the official state media then reported China's concerns in more muted language.

Sun Weide, the embassy spokesman, repeatedly declined to say whether Rice's message during the trip had unnerved the Chinese leadership. But he expressed fear that the administration's actions have undermined support for the "one China" policy that has governed U.S.-Sino relations for three decades.

"The important thing is for the United States to honor its commitments," Sun said, calling the situation across the Taiwan Strait "severely tested." Otherwise, he warned, it would harm bilateral relations and affect China's cooperation on such issues as the North Korean nuclear crisis.

The Bush administration entered office deeply suspicious of China, but has hailed the improving cooperation with China as one of its foreign policy achievements. China's decision to intensify its public criticism over Taiwan -- just seven months after President Bush alarmed conservatives by appearing to side with Beijing over Taiwan's moves toward independence -- suggested that the Chinese leadership is publicly testing the administration's commitments in this election year.

A senior administration official who had traveled with Rice played down the spokesman's comments in a conference call with reporters. "The relationship with China, while we are not wearing rose-colored glasses, is productive and stable," he said, speaking on the condition of anonymity under guidelines set by the White House.

The official said Rice heard even stronger language on Taiwan during her meetings in Beijing. Top leaders warned that they will "not sit idly by" if arms sales to Taiwan went forward, and said that Taiwan is "an obstacle" to U.S.-Chinese relations.

The official said Chinese officials appear to believe that the administration's policies on human rights, democracy, Hong Kong and other issues "added up" to a policy "aimed at regime change in Beijing." To allay those concerns, Rice, in her meetings, "conveyed that we do not want a weak China," he said. "We want a more confident and transforming China that the rest of the region would welcome."

Vice President Cheney, during a trip to Beijing in April, also tried to calm Chinese fears over the nascent independence movement in Taiwan. But Cheney pointedly noted that how Beijing handles Hong Kong -- which was returned to China in 1997 after a century of British colonial rule -- could influence the situation in Taiwan.

Sun yesterday rejected Cheney's statement as "interference from the U.S. government." He said that "you know, I know and everyone knows before 1997 there was no democracy. Democracy has been expanding in Hong Kong over the years" since Beijing took control.

The U.S. official who traveled with Rice said Chinese officials had told Rice during the discussion on Hong Kong that "you, too, suffered under the British colonial yoke." Rice, he said, made clear to the Chinese that although the United States is not challenging the "basic law" that set up Chinese authority over Hong Kong, "we have fundamental concerns about the civil liberties" in the former colony.

China claims sovereignty over Taiwan and has threatened to seize it by force if necessary. Taiwan's newly reelected president, Chen Shui-bian, says the island is an independent country.

The U.S. official said Rice noted to the Chinese leaders that Chen muted his rhetoric in his inauguration speech, and that this "represented a chance for dialogue." But although he said the Chinese leaders acknowledged that Chen had modified his language, they are "convinced he is faking it," and "their distrust of Chen is visceral," the official said.

Rice told the Chinese leaders that the U.S. arms sales were largely in response to China's missile buildup across the Taiwan Strait, but the U.S. official said Chinese officials did not directly respond to this point. They noted instead that China's defense budget is small compared with that of the United States.

Sun said that China believes one of the three communiques that governs U.S.-China bilateral relations, signed in 1982, requires the United States to reduce its arms sales to Taiwan, and "we think it is time for the United States to honor its commitments to the Chinese side."

President Ronald Reagan, who signed the communique, at the same time secretly signed a one-page memorandum saying that he believed the communique restricted U.S. arms sales only if the balance of power between Taiwan and China was preserved -- and so the United States could help Taiwan if China improved its military capabilities.

On the North Korean impasse, Sun also broke new ground at the news conference. He said China, along with other participants in the North Korean talks, believes the United States must reward North Korea with "corresponding measures" at the moment Pyongyang declares it has frozen its nuclear activities. The United States has insisted it will not provide such incentives until North Korea's full disclosure of its programs has been verified by U.S. intelligence.

National security adviser Condoleezza Rice, meeting government officials in China last week, rejected demands that the U.S. curb arms sales to Taiwan. Chinese leaders said that they would "not sit idly by" if the sales go through.