The United States slammed Taiwan's President Ma Ying-jeou after he announced he would visit a disputed island in the South China Sea on Thursday, criticising the plan as "extremely unhelpful" in a region rife with tension.

Wednesday's announcement of the visit came weeks after Taiwanese coastguards drove off a Vietnamese fishing boat near Taiping Island, a Taiwan-administered islet in the Spratly archipelago.

The chain is claimed in part or whole by Vietnam, China, the Philippines, Malaysia and Brunei.

"We are disappointed that President Ma Ying-jeou plans to travel to Taiping Island," said Sonia Urbom, spokeswoman of the American Insitute in Taiwan, the de facto US embassy.

"Such an action is extremely unhelpful and does not contribute to the peaceful resolution of disputes in the South China Sea," she said.

The US is Taiwan's main ally and a key arms supplier but has repeatedly said it does not want to see an escalation of tensions in the region.

Taiwan said earlier Wednesday it wanted to reaffirm its sovereignty of Taiping.

"Taiping Island is an inherent part of the Republic of China's territory," said Charles Chen, spokesman for the presidential office, using the official name for Taiwan.

The purpose of the trip was to visit Taiwanese personnel stationed there ahead of the Lunar New Year holiday, Chen said.

China, which sees Taiwan as part of its territory and claims almost all of the South China Sea, offered a measured response to the visit.

Although Taiwan is self-ruling after splitting with the mainland in 1949 following a civil war, Beijing still sees it as part of "one China" to be reunited.

"It is a joint responsibility and duty of compatriots in the mainland and Taiwan to safeguard state sovereignty and territorial integrity," said Ma Xiaoguang, spokesman for China's Taiwan Affairs Office, according to official state news agency Xinhua.

The only time a Taiwanese president has visited Taiping Island was in 2008, when former leader Chen Shui-bian went.

Ma, of the China-friendly ruling Kuomintang, has less than four months left of his term and will be succeeded by Tsai Ing-wen of the opposition Democratic Progressive Party (DPP), who won presidential elections in a landslide victory earlier this month.

The presidential office invited Tsai to join the trip, but the DPP said it did not plan to send any representative.

Taiwan has been boosting its presence in Taiping, the largest island in the Spratlys.

It inaugurated a solar-powered lighthouse, and expanded an airstrip and a pier on the island late last year.

China is seen by other Spratly claimants as the biggest threat in the South China Sea.

Separately, Taiwan conducted military drills Tuesday and Wednesday in the face of growing fears that tensions with the mainland will escalate in the wake of Tsai's election.

The DPP is traditionally a pro-independence party and relations with Beijing are likely to cool following a rapprochement under the KMT.