China claims Taiwan as part of its territory and has intensified political and military pressure on the self-ruled democratic island in recent years.

The poll carried out last month was commissioned by the Institute for National Defense and Security Research and released ahead of Taiwan's National Day on Thursday, when President Lai Ching-te is due to deliver a speech.

China maintains a near-daily military presence around Taiwan and has held three rounds of large-scale war games in the past two years in which it sent warplanes and ships to encircle the island.

CIA director William Burns said last year that Chinese President Xi Jinping had ordered his military to be ready to carry out a successful invasion of the island by 2027.

In the event of a Chinese attack, 67.8 percent of the 1,214 people surveyed said they would be "very willing or somewhat willing" to fight in defence of Taiwan, while 23.6 percent said they would not be.

Nearly 64 percent of respondents considered China's "territorial ambition" a "serious threat". However, Yet 61 percent believed China was unlikely to launch an attack in the next five years.

Lee Wen-chung, chief executive of the Taipei-based think tank, said the 2027 timeline for a potential Chinese invasion was based on when Xi may seek a fourth term.

"In order to successfully obtain the governing power for the fourth time in 2027, he may adopt relatively tough measures," Lee said.

More than 52 percent of respondents believed the United States, Taiwan's key ally and biggest arms provider, would send troops to help defend it against a Chinese invasion.

But only around 40 percent thought Washington would deploy its navy "to break" a Chinese blockade of Taiwan.

US Vice President Kamala Harris, the Democratic presidential candidate, said in a recent interview Washington "should not seek conflict" with China and declined to say whether Washington would use military force to support Taiwan if China were to attack.