• Experts in the US and Taiwan were asked which actions by China might prompt a US military response.

• US-based survey respondents indicated the US would respond if China moved to restrict Taiwan's trade.

• Majorities expected the US to respond to a civilian-led trade quarantine or to a military blockade.

The threshold for US military intervention in Taiwan likely isn't an invasion from China but a lesser action, such as Beijing restricting the island's trade, according to a loose consensus from leading experts in the US.

That's based on a report from the Center for Strategic and International Studies, a Washington, DC, foreign-policy think tank. The report was released on January 22.

For its report, titled "Surveying the Experts: US and Taiwan Views on China's Approach to Taiwan," the center polled 52 US experts, identifying them as academics, people with extensive experience in the US government, and think-tank experts who had testified before Congress.

Sixty-three percent of those surveyed said they were at least "moderately confident" the US military would step in should Beijing enact a quarantine, per the report.

The report defined a quarantine as cordoning off Taiwan's flow of goods through non-military means. An example would be the use of a strict customs-inspection regime that squeezes maritime traffic to the island's ports.

Separately, seventy-nine percent of the US experts said they were at least "moderately confident" that a naval blockade, in which China would encircle the island with its forces, would also prompt the US military to act.

That majority rises to 88% if the blockade includes Beijing launching strikes on Taiwan, per the report.

Almost all of the surveyed US experts — 96% — said the US would join the fight if China were to fully invade Taiwan.

The CSIS report noted that a quarantine or blockade could be the precursor to a full amphibious invasion by the People's Liberation Army.

Experts aren't confident US allies will get involved

The experts weren't as confident that US allies would jump into the conflict. Only 29% said they were at least "moderately confident" a quarantine would lead to a US-led multinational effort to defend Taiwan, while 33% said they were confident a blockade without strikes would create a coalition response.

Meanwhile, 60% of the experts said they were confident US allies would assist militarily if China were to invade the island.

CSIS also surveyed 35 experts and scholars from Taiwan, who were less optimistic about US intervention.

Forty percent expressed confidence that the Pentagon would aid Taipei if China were to enact a quarantine, while 60% said they were confident the US military would help in response to a blockade.

And 72% said they believed the US would step in if China invaded.

When asked how long they thought Taiwan could hold off China without the US military in the event of a blockade, 90% of the US experts said "2 weeks to 1 month" or longer, and 89% of the Taiwanese experts said the same.

Six percent on both sides said they believed a lone Taiwan could last a year.

These experts were polled from November to December 2023, CSIS said, a time when US-China relations were fraught with tension and after President Joe Biden met personally with China's leader, Xi Jinping, in San Francisco for the APEC 2023 summit.

Both leaders highlighted areas of cooperation in a rare positive sign for international ties, but the strain continues to build as Taiwan — a major flash point for a US-China war — elected William Lai Ching-te of the Democratic Progressive Party as its president.

Lai's party, under the outgoing Tsai Ing-wen, has long been opposed to Beijing's attempts to pressure Taiwan into unification.

His political victory signals the island will continue to resist and provoke Beijing, which has simultaneously grown increasingly hostile in the last decade under Xi.