Taiwan "should pay" the United States for defence, US presidential candidate Donald Trump said in a wide-ranging interview that has cast doubt on the relationship between Washginton and Taipei should he be re-elected in November.

In an interview with Bloomberg Businessweek published on Tuesday, the former president was asked if he would defend self-ruled Taiwan from China, which claims the island as part of its territory.

"I know the people very well, respect them greatly. They did take about 100 percent of our chip business. I think, Taiwan should pay us for defense," he said, according to a transcript released by Bloomberg.

"You know, we're no different than an insurance company. Taiwan doesn't give us anything."

While Washington does not diplomatically recognise the island, it is a key partner and major weapons provider to Taipei, and recently passed a multi-billion-dollar military aid package aimed at countering Beijing in the region.

Taiwan is also a major powerhouse in the crucial semiconductor industry, producing the majority of the advanced microchips needed to power the global economy.

A leader in the field is Taiwan Semiconductor Manufacturing Company (TSMC), which has been a key beneficiary of Washington's Chips and Science Act -- passed in 2022 to attract companies to invest in building chip factories on American soil.

Thanks to the law, TSMC is building two plants in the United States and announced plans for a third in April, bringing its total investment up to $65 billion.

Trump lamented in the interview that Washington was "giving them billions of dollars to build new chips in our country, and then they're going to take that too".

"I don't think we're any different from an insurance policy. Why? Why are we doing this? They took almost 100% of our chip industry, I give them credit," he said.