By Andrew Quinn
NUSA DUA, Indonesia (Reuters) - The United States called on Saturday on rivals in the disputed South China Sea to back up territorial claims with legal evidence -- a challenge to China's declaration of sovereignty over vast stretches of the region.
"We also call on all parties to clarify their claims in the South China Sea in terms consistent with customary international law," Secretary of State Hillary Clinton said in remarks at Asia's largest security conference.
"Claims to maritime space in the South China Sea should be derived solely from legitimate claims to land features," she said. The South China Sea row has taken center stage at this week's meeting of the ASEAN Regional Forum on the Indonesian island of Bali, where the United States, China and Southeast Asian nations have discussed the future of the potentially resource-rich region.
China, Taiwan, and four ASEAN members -- the Philippines, Malaysia, Brunei and Vietnam -- all claim territory in the South China Sea, while Washington has irritated Beijing by declaring it also has a national interest at stake in ensuring freedom of navigation and trade.
China's claim is the biggest and Beijing says it has had undisputable sovereignty over the South China Sea since ancient times.
Beijing on Thursday agreed to take preliminary steps with its Southeast Asian nations to establish a "code of conduct" for the South China Sea, a step Clinton said could ease tensions that have rattled the region as disputes between China, Vietnam and the Philippines heat up.
But she indicated on Saturday that the United States would push for more clarity on the subject, suggesting that all nations involved should delineate their claims according to the 1982 international Law of the Sea.
The Philippines also said China's claims had no validity under international law.
U.S. officials said many of the national claims to territory in the region were exaggerated, and that many nations had also preferred to legitimize claims based on historical precedent rather than land features.
Clinton said the United States had no claim to the South China Sea, and took no position on the relative merits of competing claims.
But she said the United States, as a maritime nation, did have an interest in ensuring that disputes were resolved peacefully, and called on all countries involved to avoid exacerbating the situation.
"They should exercise self-restraint in the conduct of activities that would complicate or escalate disputes ... including, among others, refraining from taking action to inhabit presently uninhabited islands, reefs, shoals, cays, and other features, and to handle their differences in a constructive manner," she said.
A senior U.S. official said Clinton's move to invoke the Law of the Sea convention to assess claims could require many countries to dig for solid evidence to back up their territorial assertions.
The United States itself has signed but not ratified the Law of the Sea.
But regional claimants -- excluding Taiwan, which Beijing views as a renegade province and blocks from almost all formal international agreements -- do belong to the convention, although there remains no clear international procedure for adjudicating rival claims.
"The truth is that almost all claimants in the South China Sea have exaggerated claims so this is something that frankly will cause all the various countries to have to look very carefully at their overall approach," the official said, adding that overlapping claims to land features could complicate the issue. "As a first step, greater clarity and precision around both claims and the legal foundation for those claims we think would serve as an important confidence-building step."
(Editing by Daniel Magnowski and Yoko Nishikawa)