Taiwan pledged Wednesday to build up its military in the face of an increased risk of invasion by China in a major defence ministry report that comes as ties with Beijing worsen.

China still sees Taiwan as part of its territory to be brought back into its fold, by force if necessary, even though the island has been self-governing since the two sides split after a civil war in 1949.

Beijing is deeply suspicious of president Tsai Ing-wen, whose Democratic Progressive Party is traditionally pro-independence.

Taiwan has never declared formal independence and last week China's premier Li Keqiang said authorities would not tolerate "any attempts to separate Taiwan from the motherland".

It has severed all official communications with Taipei since Tsai became leader in May and has reportedly discouraged Chinese visitors from travelling to the island.

In a summary of a four-yearly report to be delivered to parliament Thursday, Taiwan's defence ministry said it wanted to build a bolstered "multi-layer defence front" including submarines, missiles and drones which it hoped would act as a deterrent.

If there was still an attempted invasion, combined interception forces would "weaken the enemy's capabilities and crush its attacks to deter it from landing on the island".

The report summary said Beijing had never given up on its desire to invade.

"Preparing for a war to invade Taiwan is a major goal of its military preparation," the summary said.

It added China's military expenses had been growing and its resources had seen "rapid modernisation".

In contrast, Taiwan had limited capabilities and was suffering from a lack of soldiers.

To address its weaknesses, the island would focus on developing three key areas ─ aerospace, shipbuilding and information security ─ and would seek to develop more of its own weapons, the ministry said.

Beijing sent its only aircraft carrier, the Liaoning, through the Taiwan Strait in January as a show of strength, but it did not enter Taiwanese waters.

Since then Taiwan has announced a ramping up of its military, including the development of new stealth fighter jets and a locally built fleet of jet trainers.

Currently the United States, its most powerful ally, is its main arms supplier, even though the two sides do not have official diplomatic ties after Washington switched recognition to Beijing in 1979.

There have been concerns Taiwan will become a bargaining chip between the US and China since President Donald Trump angered Beijing with a protocol-busting telephone conversation with Tsai following his election victory.

Trump and China's president Xi Jinping subsequently smoothed over the dispute in a phone call in which the US leader reiterated Washington's adherence to the "one China" policy that nominally endorses Beijing's claim to Taiwan.

China and the United States are currently discussing arrangements for a summit between Trump and Xi.

The defence ministry report made little mention of US ties, saying only that the US "maintains its deployment in Asia Pacific" and conducts military drills with allies.