TAIPEI, April 19 (Reuters) - Taiwan is seeking to acquire long-range, air-launched cruise missiles from the US, a defence official said on Monday (Apr 19), as the Chinese-claimed island bolsters its forces in the face of increasing pressure from Beijing.

While Taiwan is developing its own long-range missiles, to give it an ability to strike back deep into China in the event of war, it has also looked to the US to help provide it more advanced weaponry.

Asked in parliament which weapons systems Taiwan wants to buy but the US has not yet said it can, Lee Shih-chiang, head of Taiwan's defence ministry's strategic planning department, named Lockheed Martin Corp's AGM-158.

"We are still in the process of seeking it" from the US, Lee said. "Communication channels are very smooth and normal."

He did not elaborate.

The AGM-158 JASSM - standing for Joint Air-to-Surface Standoff Missile - can have a range of almost 1,000km depending on the model, and be fixed to aircraft including F-16s, which Taiwan operates.

Lockheed Martin says the missile is designed to destroy high-value, well-defended, fixed and relocatable targets, and be launched far enough away to keep the launch aircraft well away from enemy air defence systems.

China has stepped up military activity near Taiwan, as it tries to force the government in Taipei to accept Beijing's claims of sovereignty.

Taiwan's armed forces, dwarfed by China's, are in the midst of a modernisation programme to offer a more effective deterrent, including the ability to hit back at bases far from China's coast in the event of a conflict.

Taiwan's armed forces have traditionally concentrated on defending the island from a Chinese attack.

But President Tsai Ing-wen has stressed the importance of developing an "asymmetrical" deterrent, using mobile equipment that is hard to find and destroy, and capable of hitting targets far away from Taiwan.

Washington, Taipei's main foreign arms supplier, has been eager to create a military counterbalance to Chinese forces, building on an effort known within the Pentagon as "Fortress Taiwan".

Beijing views Taiwan as sovereign Chinese territory, and has never renounced the use of force to bring it under its control.