THE UNITED STATES has warned China to “back off” as tensions rise to flashpoint in the South China Sea.

In a statement, the US State Department cautioned China about its addition of a military garrison and civilian officials near the contested Scarborough Reef and its use of barriers to deny access to foreign ships.

These moves “run counter to collaborative diplomatic efforts to resolve differences and risk further escalating tensions in the region”, said the statement, issued early on Friday morning and attributed to Patrick Ventrell, the acting deputy spokesman.

Six countries have complex competing claims to the region’s water and islands, which are rich in fish, oil and gas and other resources.

China’s recent moves over the Scarborough Reef have ruffled feathers in several nations, including Vietnam, Japan and the Philippines. There also have been reports that China is preparing to invite oil company bids for energy exploration in the area.

Countries in the region have been trying to work out a method for peacefully arbitrating their claims through a leading regional body, the Association of South-East Asian Nations, and have urged states not to take any provocative actions.

The US statement appeared to be a sign to South-East Asian countries that the administration continues its close watch on developments in the regionBut one analyst cautioned that by singling out China at a time when several nations have been pushing claims, the Obama administration may confirm Chinese fears that it is strengthening security ties in South-East Asia to limit the expansion of Chinese power.

“It’s very likely that China will read this as unnecessary, and confirming its concerns that the US is actively seeking to line up with South-East Asia against it,” said Kenneth Lieberthal, a China specialist at the Brookings Institution and a former Clinton administration official.

Administration officials said last year they were shifting their foreign policy attention more to East Asia and have announced a series of steps to reinforce security ties with Vietnam, the Philippines, Australia and other countries.