sent dozens of warplanes over the Taiwan Strait days after Mr. Biden’s inauguration in January, the State Department released a statement declaring America’s “rock solid” commitment to the island. Mr. Biden raised the subject of Taiwan during his phone call in February with Mr. Xi, and Secretary of State Antony J. Blinken and the national security adviser Jake Sullivan raised their concerns about the island during their meeting last month in Anchorage with two top Chinese officials.

“I think people are bending over backward to say to China, ‘Do not miscalculate — we strongly support Taiwan,’” said Bonnie Glaser, the director of the China Power Project at the Center for Strategic and International Studies.

Ms. Glaser said she had been surprised at the Biden team’s early approach toward Taiwan, which so far has maintained the Trump administration’s amplified political support for the island, a posture some critics called overly provocative. She noted that Mr. Blinken had recently urged Paraguay’s president in a phone call to maintain his country’s formal ties with Taiwan, despite pressure from Beijing, and that the U.S. ambassador to Palau, an archipelago state in the Western Pacific, recently joined a diplomatic delegation from that country to Taiwan.

“That is just really outside of normal diplomatic practice,” Ms. Glaser said. “I think that was quite unexpected.”

But Ms. Glaser does not support a more explicit U.S. commitment to Taiwan’s defense. Like many other analysts and American officials, she fears that such a change in policy might provoke China.

“Maybe then Xi is backed into a corner. This could really cause China to make the decision to invade,” she warned.

billions of dollars in arms sales under the Trump administration that featured fighter jets and air-to-ground missiles allowing Taiwanese planes to strike China. Such equipment is meant to diminish Taiwan’s need for an American intervention should it come under attack.

But Mr. Colby and others say the United States must develop a more credible military deterrent in the Pacific region to match recent advances by China’s military.

Testifying before the Senate Armed Services Committee last month, H.R. McMaster, a national security adviser for Mr. Trump, said the current ambiguity was sufficient.

“The message to China ought to be, ‘Hey, you can assume that the United States won’t respond’ — but that was the assumption made in June of 1950, as well, when North Korea invaded South Korea,” Mr. McMaster said.

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