Testifying before the House Committee on Foreign Affairs' Subcommittee on Asia and the Pacific, Assistant Secretary of State for East Asia Daniel Russel listed China's actions in asserting its South China Sea claims.
They include continued restrictions on access to the Scarborough Reef, pressure on the longstanding Philippine presence at the Second Thomas Shoal, and putting hydrocarbon blocks up for bid in an area close to another country's mainland and far away even from the islands China is claiming.
"There is a growing concern that this pattern of behavior in the South China Sea reflects an incremental effort by China to assert control over the area contained in the so-called 'nine-dash line' despite the objections of its neighbors and despite the lack of any explanation or apparent basis under international law regarding the scope of the claim itself," Russel said.
Other Chinese actions include announcing administrative and even military districts in contested areas in the South China Sea and the recent updating of fishing regulations covering disputed areas in the South China Sea, Russel said.
His detailed testimony comes as the United States, as a Pacific power, seeks to strengthen its role in region as part of Asia-Pacific pivot policy.
China uses its ancient texts and its so-called historical nine-dash line maps to claim jurisdiction over vast areas of the South China Sea and its islands such as the Spratly islands and Scarborough shoal over which other countries also have claims. Besides China, other South China Sea countries are Taiwan, the Philippines, Brunei, Indonesia, Malaysia and Vietnam.
Russel said China's "lack of clarity" over its sea claims has created "uncertainty, insecurity and instability in the region," limiting the prospect for achieving a mutually agreeable resolution among the claimants.
"I want to reinforce the point that under international law, maritime claims in the South China Sea must be derived from land features. Any use of the "nine dash line" by China to claim maritime rights not based on claimed land features would be inconsistent with international law," Russel said.
He asked China to clarify or adjust its nine-dash line claim "to bring it in accordance with the international law of the sea."
Russel said an effective Code of Conduct would promote a rules-based framework for managing and regulating the behavior of the relevant countries in the South China Sea.
The senior diplomat said both the South China and East China Seas are vital thoroughfares for global commerce and energy as over half the world's merchant tonnage flows through the seas. He said more than 15 million barrels of oil per day transited the Strait of Malacca last year, with most of it continuing onward through the East China Sea to three of the world's largest economies of Japan, South Korea and China.
"A simple miscalculation or incident could touch off an escalatory cycle," he warned.
Russel also expressed U.S. concerns about the "serious downturn" in China-Japan relations stemming from their competing claims to the Japanese-controlled Senkaku islands in the East China Sea.
"We support Japan's call for diplomacy and crisis management procedures in order to avoid a miscalculation or a dangerous incident," he said.
In this context, Russel said China's setting up of an Air Defense Identification Zone over the East China Sea in November was a "provocative act and a serious step in the wrong direction."