• The US military is likely to intervene if China enacts a quarantine or blockade in China, experts say.

• A CSIS survey of 52 experts found that 63% believe a quarantine would provoke a US response.

• And 79% of those surveyed said they were at least "moderately confident" the Pentagon would step in during a blockade.

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

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

For its report, titled "Surveying the Experts: U.S. and Taiwan Views on China's Approach to Taiwan," the center said it polled 52 US experts, including academics, people with extensive experience in the US government, and think-tank experts who have testified in Congress.

About 63% of those surveyed said they were at least "moderately confident" the US military would step in should Beijing enact a quarantine, per the report.

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

A naval blockade, in which China encircles the island with its forces, would also separately be likely to prompt the US military to act, said 79% of the experts, who indicated they were at least "moderately confident" in their assessment.

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

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

A quarantine or blockade could notably be the precursor to a full amphibious invasion by the People's Liberation Army, CSIS' report said.

Experts aren't confident that US allies will get involved

However, the experts weren't as confident that US allies would jump into the conflict. Only 29% said a quarantine would lead to a US-led multinational effort to defend Taiwan, while 33% said a blockade with no strikes would create a coalition response.

Meanwhile, 60% of the experts were confident that 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% indicated the US military would help in response to a blockade.

And 72% believe the US would step in if China invaded.

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

Six percent on both sides 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 before President Joe Biden met personally with Chinese 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 flashpoint 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 that the island will continue to resist and provoke Beijing, which has simultaneously grown increasingly hostile in the last decade under Xi.