Why Taiwan arms sales, in place for decades, will remain a source of US-China tensions

Beijing and Washington appear set to remain at loggerheads over weapons sales to Taiwan, given US approval for a US$300 million tactical systems upgrade in its latest defence support for the island.

The December 15 announcement came a month after a much-awaited summit in San Francisco between US President Joe Biden and his Chinese counterpart Xi Jinping, who pointed out that Taiwan remained "the most important and most sensitive issue in China-US relations" and urged that the US "stop arming Taiwan".

Observers said the latest sale might be "less provocative" or "low-key" as it involved systems support, but would still be viewed by Beijing as a challenge to its national reunification efforts.

Do you have questions about the biggest topics and trends from around the world? Get the answers with SCMP Knowledge, our new platform of curated content with explainers, FAQs, analyses and infographics brought to you by our award-winning team.

Beijing sees Taiwan as part of China, to be reunited by force if necessary. The United States, like most countries, does not recognise self-governed Taiwan as independent, but is opposed to any attempt to take the island by force.

Washington is also legally bound under its 1979 Taiwan Relations Act to help the island protect itself, by providing "arms of a defensive character", and is its top international supporter and weapons supplier.

The act, passed three months after Washington switched diplomatic recognition to Beijing in January 1979, aimed to demonstrate that the US was not abandoning its old ally. But it is deliberately ambiguous about Washington's commitment to directly defend the island against an attack from Beijing - seen as aimed at discouraging supporters of Taiwan independence.

According to the Pentagon, the tactical systems sale would include follow-on life cycle support to maintain Taiwan's C4 capabilities - involving command, control, communications and computers.

Dean Chen, a professor of political science at Ramapo College of New Jersey, compared the latest deal to those announced under Biden's predecessor, Donald Trump.

"The nature of the arms sale this time - to merely do a follow-on life-cycle support of Taiwan's C4 capabilities - is relatively less provocative than, say, the Trump 2019 sales," Chen said.

Trump's approval in 2019 for an US$8 billion arms sale to Taiwan involving 66 F-16 fighter jets was one of the largest single such transactions. It also came five months ahead of presidential elections in Taiwan in January 2020, when Tsai Ing-wen of the independence-leaning Democratic Progressive Party was re-elected for a second and final term.