TAIPEI, Dec 27 (Reuters) - Taiwan will announce on Tuesday a plan to extend compulsory military service to one year from the current four months, according to a senior government official, as the island deals with rising Chinese military pressure.

The office of Taiwan President Tsai Ing-wen said she will call a national security meeting on Tuesday morning to discuss reinforcing the island's civil defence, followed by a news conference on unspecified new civil defence measures.

The official Central News Agency, citing government and ruling party sources familiar with the matter, reported late on Monday that her government would on Tuesday announce the plan to extend compulsory military service and that the new system would go into effect in 2024.

Taiwan has been gradually shifting from a conscript military to a volunteer-dominated professional force, but China's growing assertiveness towards the island it claims as its own, as well as Russia's invasion of Ukraine, have prompted debate about how to boost defence. Russia calls the war a "special operation".

Taipei, which rejects Beijing's sovereignty claims, on Monday reported the larges-ever Chinese air force incursion into the island's air defence identification zone, with 43 Chinese planes crossing an unofficial buffer between the two sides.

China also staged war games near Taiwan in August following a visit to Taipei by then-U.S. House Speaker Nancy Pelosi.

Previous governments under the ruling Democratic Progressive Party and the main opposition Kuomintang cut compulsory service for men from more than two years to four months to please younger voters as tensions eased between Taipei and Beijing.

Tsai is overseeing a broad modernisation programme, championing the idea of "asymmetric warfare" to make the island's forces more mobile, agile and harder to attack.

China has stepped up its diplomatic, military and economic pressure in recent years on the self-governed island to accept Beijing's rule. Taiwan's government says only Taiwanese people can decide their future and vows to defend itself if attacked. (Reporting By Yimou Lee and Ben Blanchard. Editing by Gerry Doyle)