The United States is concerned that recent incidents in the South China Sea threaten the peace and stability on which the remarkable progress of the Asia Pacific region has been built," US Secretary of State Hillary Clinton told a security forum in Indonesia.
"These incidents endanger the safety of life at sea, escalate tensions, undermine freedom of navigation, and pose risks to lawful unimpeded commerce and economic development." Clinton said.
In prepared remarks to foreign ministers at the ASEAN Regional Forum, Clinton also warned all the rival claimants to the strategically vital South China Sea against using force to bolster their positions.
"Each of the parties should comply with their commitments to respect freedom of navigation and over-flight in the South China Sea in accordance with international law, to resolve their disputes through peaceful means, without resorting to the threat or use of force," she said.
China, the Philippines, Vietnam, Malaysia, Brunei and Taiwan have overlapping claims to all or parts of the sea, including hundreds of islets and reefs mostly located in the Paracel and Spratly archipelagos.
The sea is believed to be extremely rich in oil and gas deposits, as well as being where shipping lanes link East Asia with Europe and the Middle East.
The area has long been considered one of Asia's potential military flashpoints, and in 1998 Vietnam fought a brief naval battle with China on one of the reefs that left 50 Vietnamese sailors dead.
In recent months, the Philippines and Vietnam have expressed anger over what they call China's increasingly aggressive actions in the sea, such as harassing fishermen and oil exploration vessels.
Philippine Foreign Secretary Albert del Rosario said in Bali on Saturday his country had "suffered at least seven aggressive intrusions" in the disputed waters since February.
These included Chinese forces shooting at Filipino fishermen, deploying navy patrol boats to intimidate an oil exploration vessel and placing markers on some of the islets.
Del Rosario said China's actions appeared motivated by a hunger for the region's natural resources, and were heightening fears about how the country intended to treat its neighbours as its military and economic might expanded.
"I think there is that concern that China is becoming more powerful," del Rosario told AFP.
"We support their progress and their growth... but at the same time it is our expectation that their strength and their growth and their influence will be exercised in a responsible way."
Chinese Foreign Minister Yang Jiechi responded to the renewed pressure by insisting that China would work to ensure the tensions did not escalate into conflict.
"South China Sea and Asia as a whole are peaceful and stable, and this will continue through our joint efforts," Yang told reporters on the sidelines of the forum.
"China will continue to contribute to peace and stability in Asia."
At a meeting with the 10 members of the Association of Southeast Asian Nations in Bali on Wednesday, China also agreed to a set of guidelines setting a framework for an eventual code of conduct for the sea.