The White House said on Wednesday that a dispute between China and Vietnam that erupted within days of President Barack Obama's visit to Asia to address regional tensions needs to be resolved with dialogue, not intimidation.
While the United States was not a party to the dispute, White House spokesman Jay Carney said Obama had repeatedly stressed on his trip last month the need for peaceful dialogue on various disputes involving China and the South China Sea.
The renewed tension between Vietnam and China underscores one of the biggest challenges in Asia facing Obama, who is under pressure by America's allies to accelerate a "pivot" of military assets to the region to counter China's rising influence.
Russia's annexation of Ukraine's Crimea peninsula - and perceptions of limited U.S. options to get Moscow to back down - have heightened unease in parts of Asia over whether Beijing will be emboldened to use force to pursue its territorial claims in the East and South China Seas.
The standoff in the South China Sea and anti-China violence in tightly controlledVietnam have raised fears of an escalation in tensions between the Communist-ruled neighbors, which fought a brief but bloody border war in 1979.
Such disputes "need to be resolved through dialogue, not through intimidation," Carney told a regular briefing. "We again urge dialogue in their resolution."
An Asian diplomat said it was important that Washington took a firm line with Beijing while also using its influence with Vietnam to calm the mood.
He said the concern among Southeast Asian countries was that China was seeking incremental gains in provoking a series of crises with its neighbors, a tactic that could eventually change the regional landscape unless it was met with a resolute response.
Thousands of Vietnamese set fire to foreign factories they believed to be Chinese on Tuesday in an angry reaction to Chinese oil drilling in a part of the South China Sea claimed by Vietnam, officials said.
The confrontation blew up after China moved a giant oil rig into an area of the South China Sea also claimed by Vietnam. Dozens of ships from both countries are around the rig and the two sides have accused each other of intentional collisions, increasing the risk of open confrontation.
The U.S. State Department said it was monitoring events in Vietnam closely, and urged restraint from all parties, while adding: "We support the right of individuals to assemble peacefully to protest."
The White House statement comes as Obama's policy toward Asia has come under some criticism at home for being more rhetoric than substance.
The current crisis erupted within days of a week-long visit to Asia by Obama in late April in which he pledged that Washington would live up to its obligation to defend its allies in the region.
The foreign minister of Singapore, a close U.S. ally and one of Vietnam's partners in the Association of Southeast Asian Nations (ASEAN), said in a speech in Washington on Tuesday that China's rapid rise had already changed the regional dynamic.
"I note that the U.S. is trying to urge all claimants not to resort to aggression and has called for a reduction of tensions," the minister, K. Shanmugam, said.
"To some extent, this reflects the new reality. The U.S. now needs the co-operation of others and asks for it. As opposed to the post World War Two situation, when the U.S. could impose its will."
Ernest Bower, of the Center for Strategic and International Studies think tank, called the violence in Vietnam "troubling" and the risk of escalation real.
"I think either China or Vietnam will find a way to back down from this one ... or I think you do end up with some sort of conflict," he said.
Vietnamese resentment against China runs deep, rooted in feelings of national pride and the struggle for independence after decades of war and more than 1,000 years of Chinese colonial rule that ended in the 10th century. Chinese forces invaded northern Vietnam in 1979 and border skirmishes continued into the 1980s.
(Reporting by Steve Holland and Mark Felsenthal; Editing by Bill Trott and Eric Walsh)