The United States' top diplomat on East Asia has suggested China's wide-ranging territorial claims in the South China Sea do not comply with international law and should be clarified or adjusted.
China claims nearly the entire 3.5-million square kilometer South China Sea, by virtue of what it sees as its historical rights within the so-called nine-dash line. Vietnam, the Philippines, Taiwan, Malaysia and Brunei also claims parts of the region.
In congressional testimony Wednesday, U.S. Assistant Secretary of State for East Asian and Pacific Affairs Danny Russel said any use of the nine-dash line to claim maritime rights must be based on land features, such as a nation's coastline or its islands.
"Any Chinese claim to maritime rights not based on claimed land features would be inconsistent with international law. China could highlight its respect for international law by clarifying or adjusting its claim to bring it into accordance with international law of the sea," said Russel.
Russel also said that there were "growing concerns" that China is trying to gradually assert control over the area, despite objections by its neighbors. He cited several Chinese actions that recently have "raised tensions."
"This includes continued restrictions on access to the Scarborough reef, pressure on the longstanding Philippine presence at the Second Thomas Shoal and the recent updating of fishing regulations covering disputed areas in the South China Sea. Our view is that these actions have raised tensions in the region and have exacerbated concerns about China's long term strategic objectives," said Russel.
Russel also raised fresh U.S. concerns over China's activities in the East China Sea, where Beijing recently set up an Air Defense Identification Zone in an area also claimed by Japan.
He called the move a "step in the wrong direction," and warned China against setting up a so-called ADIZs elsewhere.
"We neither recognize nor accept China's declared ADIZ. The United States has no intention of changing how we conduct our operations in the region. And we've made clear to China that it shouldn't attempt to implement that ADIZ and should refrain from taking similar actions elsewhere in the region," said Russel.
Russel said he was also concerned about the "serious downturn" in relations between Japan and China. He said neither Beijing, Tokyo, nor the global economy could afford an unintended clash between the two countries.
He also said he supports Japan's call for diplomacy and crisis management procedures to help avoid a conflict.
The U.S. has said it does not take a position on any of the individual maritime disputes, but is only interested in helping find peaceful resolutions and ensuring freedom of navigation and commerce.
China has also said it is seeking a peaceful resolution, but has rejected attempts to solve the disputes in multilateral forums, such as the Association of Southeast Asian Nations. It instead prefers to deal individually with each nation, giving it a strategic advantage.
Beijing is also skeptical of the Obama administration's so-called military and economic "rebalancing" toward the Asia-Pacific, viewing the policy as an attempt to contain its rise.
Interactive Map of China, Japan, South Korea Air Zones