Taiwan's defence ministry said it feared coastguards now stationed in the Spratlys, claimed by several nations, and the Pratas islands, claimed by China, may not be sufficiently heavily-equipped to handle potential conflicts.

"Currently the coastguards in the Nansha (Spratlys) and Tungsha (Pratas) are only armed with light weapons," Taiwan's defence ministry spokesman David Lo told AFP.

"The missile boats and tanks is an option we've offered to the coastguards," he said, without specifying numbers and adding that the coastguard had yet to make a final decision.

Local media said the missile boats' presence would serve as a deterrent.

Each of Taiwan's 47-tonne Seagull class boats is armed with two Hsiungfeng I missiles, a ship-to-ship weapon with a range of 40 kilometres (24 miles).

The remarks come as China becomes increasingly assertive in the potentially resource-rich South China Sea, following several years of relative quiet.

Taiwan on Saturday reiterated its claims to the Spratlys, along with three other island groups in the South China Sea, amid a flare-up in regional tensions over rival claims.

Taiwan, Vietnam, Brunei, China, Malaysia, and the Philippines claim all or part of the Spratlys, which could lie on top of large oil reserves.

The Taiwanese coastguard currently has a 130-strong garrison on Taiping, the biggest island in the Spratlys archipelago, which has a runway to smooth logistical support.

The Philippine military in April said it planned to use a new US-made vessel to boost patrols in the disputed waters, after a complaint about Chinese patrol boats harassing a Philippine oil exploration vessel in the area.

"We've been troubled by some of these reports about the South China Sea and believe they only serve to raise tensions and don't help with the peace and security of the region," said State Department spokesman Mark Toner.

"We support a collaborative diplomatic process... and call on all claimants to conform all of their claims, both land and maritime, to international law."

He said the United States and the international community at large share an interest in maintaining maritime security in the region, citing freedom of navigation, economic development and respect for international law.

Beijing says it is committed to peace in the South China Sea, but its more assertive maritime posture has caused concern among regional nations.

Tensions between China and Vietnam are at their highest level in years after Hanoi accused Chinese marine surveillance vessels of cutting the exploration cables of an oil survey ship in May inside its exclusive economic zone in the maritime waters.

On Thursday, Vietnam alleged a similar incident in the zone, saying a Chinese fishing boat rammed the cables of another oil survey ship in its waters.

Beijing countered by warning Vietnam to halt all activities that it says violate its sovereignty in disputed South China Sea waters.

The two countries have long-standing disputes over the potentially oil-rich Paracel and Spratly archipelagos and surrounding sea.

Tensions have also risen this year between China and the Philippines, another claimant to the Spratly islands, where Malaysia, Brunei and Taiwan also say they have a stake.

Vietnam's navy on Friday announced it will hold a live-fire drill in the South China Sea next week.

"We don't support anything that adds to raising the current level of tension; we don't think it's helpful," Toner said.

"What there needs to be is a collaborative diplomatic process, a peaceful process, to resolve various territorial disputes and otherwise," he added. "Shows of force, other gestures like that, just I think raise tensions."

US Defense Secretary Robert Gates warned last weekend that clashes may erupt in the South China Sea unless nations with conflicting territorial claims adopt a mechanism to settle disputes peacefully.