The Bush administration is embracing a closer political and military relationship with Taiwan than any U.S. government in decades as a way of endorsing democracy on the island and deterring a Chinese military threat across the Taiwan Strait, administration officials and analysts said.

U.S. officials are now debating questions that were once taboo, such as a visit to Washington by President Chen Shui-bian and the establishment of secure military communications between U.S. and Taiwanese forces, government and congressional sources said. The Pentagon has also built up U.S. forces in the Pacific and has formulated detailed plans to respond to a crisis in the Taiwan Strait, defense officials said.

More broadly, the tone of U.S. relations with Taiwan has changed, prompting Taiwan's chief representative to the United States, C.J. Chen, to observe that ties are the strongest since 1979, when Washington broke relations with Taipei in favor of Beijing.

"Taiwan is not looked at as a problem anymore," a State Department official said. "We look at it as a success story."

The U.S. moves toward Taiwan are complicating relations with China. Hu Jintao, China's vice president and presumptive next leader, is expected to issue a tough statement on Taiwan after arriving in Washington today on an important visit. Beijing claims that the island of 23 million people, arguably Asia's most vibrant democracy, belongs to China and says it would attack Taiwan if it were to declare independence.

For years, U.S. administrations maintained "strategic ambiguity" toward Taiwan, a stance meant to discourage Taiwan from declaring independence while keeping Beijing guessing about how the U.S. would respond to a Chinese offensive. President Bush signaled a shift in this approach early in his term when, in an interview with ABC, he committed the United States to "whatever it took" to help Taiwan defend itself.

Although Bush administration officials said at the time that U.S. policy had not changed -- and Bush reiterated the ambiguous stance during a trip to Beijing in February -- administration officials acknowledge a shift.

"Our ambiguity on Taiwan has become less ambiguous," a senior administration official said.

Some analysts said that the U.S. approach to Taiwan risks a confrontation with China. They warn that once in power next year, Hu would be under pressure to prove his nationalist credentials by challenging the United States. Bush administration officials, however, argued that Chinese officials are wary of U.S. military power and concerned about maintaining the U.S. export market and American investment and high technology. The officials said the Chinese government's protests so far have been relatively weak: the cancellation of two naval port calls.

"I can't imagine Hu Jintao and his cohorts, faced with large-scale unemployment and splits within the leadership, deciding to have a crisis in the Taiwan Strait and [have] the U.S. stare them down," the senior administration official said.

The Bush administration's new policy toward Taiwan has its roots in a crisis that roiled the waters of the Taiwan Strait in 1995-96.

The Clinton administration was forced by a congressional resolution to allow Taiwan's president at the time, Lee Teng-hui, to travel to the United States. In response, China conducted missile tests near Taiwan's two major ports, prompting the United States to dispatch two aircraft carrier battle groups to the region, bringing the two countries closer to conflict than at any time since the Korean War.

From that moment on, Pentagon planners began to take seriously China's threats to attack the island and to watch with concern China's military buildup. China has increased the number, and improved the accuracy, of missiles in the provinces facing Taiwan -- 600 are expected to be deployed by 2005. Years of double-digit increases in defense spending have helped broaden China's ability to wage war.

The 1995-96 crisis also convinced Pentagon officials that their military relationship with Taiwan needed new attention. "During the crisis I remember we were looking at overhead pictures of the PLA," recalled a former Pentagon official, referring to China's People's Liberation Army. But, he said, "We didn't know what [the Taiwanese] were doing."

In 1997, the United States began a dialogue with Taiwan about its defense needs for the first time since 1979, when Congress approved the Taiwan Relations Act. Washington is mandated under the act to help Taiwan with its defense, but no previous administration had looked seriously at Taiwan's military.

The Pentagon commissioned a series of studies by the Joint Chiefs of Staff, the Pacific Command and research groups on Taiwan's air defense, naval defense and its capabilities to counter a blockade or invasion. U.S. military officers began traveling to Taiwan and urging the government to reform its military.

The policy was controversial within the Clinton administration and precipitated bureaucratic battles between its initiator, Kurt Campbell, then the deputy assistant defense secretary for Asian and Pacific affairs, and officials in the National Security Council, who opposed closer U.S. ties to Taiwan and argued that China was strategically more important.

But by the time the studies were finished, Clinton was out of office and a new team closer to Taiwan had come to power.

The studies played a major role in helping the Bush administration decide last April to offer Taiwan its biggest arms package since 1992, worth an estimated $4 billion. Key among those items were eight diesel-electric submarines, something previous administrations had refused Taiwan because they were considered offensive weapons.

Initially, Chinese analysts viewed that offer as purely political, because the United States no longer builds diesel submarines and European manufacturers had said they would not produce the vessels for Taiwan. Next month, however, the Pentagon plans to dispatch a team of naval officers to present construction and design options to Taipei's military, a Pentagon official said.

"It was a good-faith offer and we're trying to carry through on it," the senior Bush administration official said.

Several members of Bush's new team have been intimately involved in Taiwan's security for years. In addition to a dialogue between the Pentagon and Taiwan's military, in 1997 Campbell also initiated eight secret meetings between the United States, Taiwan and Japan, which took place in Monterey, Calif., Tokyo and near Washington, sources said.

Among the American participants were Richard L. Armitage, the deputy secretary of state, Torkel L. Patterson, who until January was Bush's National Security Council senior director for Asia, and James A. Kelly, assistant secretary of state for East Asian and Pacific affairs, participants said. "Those meetings were crucial to our understanding of Taiwan's security concerns," one participant said.

Pentagon officials are also involved in helping Taiwan reform its military, focusing on "software" issues, such as training, civilian control and a national defense law, and improving "jointness," the ability of Taiwan's fractious military services to operate together.

Late last year, the Bush administration started allowing Taiwanese military officers to attend classes at the Pentagon-funded Asia-Pacific Center for Security Studies. The Bush administration has also relaxed restrictions on U.S. military officers traveling to Taiwan.

The administration also permitted Taiwan's defense minister, Tang Yiau-ming, to travel to a private defense convention in Florida last month, where he met with Deputy Defense Secretary Paul D. Wolfowitz. Now, government sources said, the administration is considering making those contacts regular. "Next time the meeting could happen in Washington," a defense official said. At the conference, Wolfowitz committed the United States to helping Taiwan with its military modernization, something no senior defense official has done publicly in years.

"We are eager to help," Wolfowitz said in remarks made available in response to a Freedom of Information Act request. "Just as important as arms sales issues, these non-hardware or software exchanges serve very important purposes."

Following an initiative started during the Clinton administration, the U.S. military is also boosting its forces in the Pacific in order to respond quickly and powerfully to any Chinese move toward Taiwan.

Peter Brookes, deputy assistant defense secretary for Asian and Pacific affairs, said at the Florida conference that the United States is seeking to increase the number of aircraft carrier battle groups in the western Pacific and deploy several more warships and guided-missile submarines "to improve our forward deterrent posture."

Until now, U.S. Navy policy has been to maintain only one carrier battle group in the western Pacific. The Navy plans to base two Los Angeles-class nuclear-fueled attack submarines in Guam, and a third is scheduled to be based there no later than 2004.

Staff writer Thomas E. Ricks contributed to this report.