TAIPEI (AFP) - Taiwan plans to expand a pier on one of the disputed Spratly islands, officials said on Sunday, as the rest of the claimants beef up military deployment in the South China Sea.

The Coast Guard Administration has budgeted NT$19 million (S$793.300) to evaluate the project, which is part of its efforts to boost defence capabilities in the disputed area this year.

"The fund will mainly be used to do an environmental impact study near Taiping Island," a coast guard official told AFP.

The fortified island, under Taiwan's control, is the largest in the disputed South China Sea area.

The United Evening News said the expanded pier would allow port calls by the coast guard's 2,000-tonne frigates. The current pier provides facilities only to small patrol boats.

Taiwan built a 1,150-metre runway on Taiping in mid-2006, despite protests from the other countries with claims to the disputed island group.

Taiwan, Vietnam, Brunei, China, Malaysia, and the Philippines claim all or part of the potentially oil-rich Spratlys.

All claimants except Brunei have troops based on the archipelago of more than 100 islets, reefs and atolls, which have a total land mass of less than five square kilometres.

The potentially resource-rich sea, home to important trade routes, is a potential military flashpoint and there has been a string of diplomatic rows between countries with overlapping territorial claims in recent years.

The Philippines and Vietnam have complained that China is becoming increasingly aggressive in its actions in the area - such as harassing fishermen - and also through bullying diplomatic tactics.