KAOHSIUNG, April 13 (Reuters) - Taiwan unveiled a new amphibious warfare ship on Tuesday (Apr 13) that can be used to land troops and will bolster supply lines to vulnerable islands offshore China and in the South China Sea.

The 10,600-tonne Yu Shan, named after Taiwan's tallest mountain, is the latest part of President Tsai Ing-wen's ambitious programme to modernise the armed forces amid pressure from China, which claims the island as its own.

Built by state-backed CSBC Corporation Taiwan, the ship will enter service next year, and will be armed with a cannon for use against air and surface targets, anti-aircraft missiles and rapid-fire Phalanx close-in anti-aircraft and anti-missile guns.

Formally naming the new ship in the southern port city of Kaohsiung, Tsai said it represented a "milestone" in Taiwan's indigenous warship-building plans.

"I believe that this ship will certainly strengthen (the) navy's ability to fulfil its mission and further solidify our defences," she said.

CSBC Chairman Cheng Wen-lung said as well as being an amphibious warfare vessel, with space for landing craft and helicopters, it will be used for transport to Taiwan's possessions in the disputed South China Sea and offshore Taiwanese islands which lie close to the Chinese coast, long considered easy targets for China in the event of war.

"During wartime it will have an amphibious warfare mission, bringing in reinforcements and fighting to retake offshore islands," he added.

The ship has a "stealthy exterior" and electromagnetic pulse protection, Cheng said.

"It can carry out various battle missions on its own out at sea for a long time."

While Taiwan's air force has benefited from big-ticket items like new and upgraded F-16s, the navy is Tsai's next focus, with submarines in production and a launch last year of the first of a fleet of highly manoeuvrable stealth corvettes.

The new Tuo Chiang-class corvettes have been dubbed by Taiwan's navy as the "aircraft carrier killer" due to its complement of anti-ship missiles. It can also carry Sky Sword anti-aircraft missiles.

Tsai has bolstered the domestic arms industry to try to make Taiwan as self-sufficient as possible.