Self-ruled, democratic Taiwan lives under the constant threat of invasion by China, which considers the island a part of its territory, to be taken one day, by force if necessary.

Beijing's sabre-rattling has intensified in recent years under President Xi Jinping, and Russia's invasion of Ukraine deepened fears in Taiwan that China might move similarly to annex the island.

Taiwan's President Tsai Ing-wen is expected to announce the extension in military service for all adult men in a press conference at 3:30 pm (0730 GMT) following a high-level meeting on national security, the semi-official Central News Agency said.

The presidential office said Monday that a proposal to "adjust the structure" of national defence was on the agenda, without providing details.

CNA said the change would come into effect in January 2024 if the formal notice of extension is issued next month.

The prospect of a Chinese invasion has increasingly worried Western nations and many of China's neighbours.

Xi, China's most authoritarian leader in decades, has made clear that what he calls the "reunification" of Taiwan cannot be passed on to future generations.

Taiwan and China split at the end of the Chinese Civil War in 1949, and Tsai has said becoming a part of China is not acceptable to the people of the island.

Taiwan is massively outgunned in a conflict, with 88,000 ground forces compared with China's one million, according to Pentagon estimates. Beijing also has a huge advantage in military equipment.

The mountainous island would still present a formidable challenge in an invasion.

Mandatory service used to be deeply unpopular in Taiwan -- once a brutal military dictatorship that has since morphed into a progressive democracy.

Its previous government had reduced compulsory military service from one year to four months with the aim of creating a mainly volunteer force.

But recent polling showed more than three-quarters of the Taiwanese public now believes that is too short.

Taiwan has stepped up reservist training and increased its purchases of warplanes and anti-ship missiles to bolster its defences. But experts have said that is not enough.

The national security meeting in Taipei on Tuesday comes two days after Chinese military exercises near Taiwan, which were held in response to what Beijing described as "provocations" and "collusion" between Washington and Taipei.