Washington is openly challenging Beijing's claims that the South China Sea is an area of China's "core interest" and that foreign powers should not intervene in the fast-rising quasi-superpower's sphere of interest. It is the first time that the US has indicated its readiness to play a major role in defusing one of Asia's hottest flashpoints.

Speaking over the weekend in the 27-member ASEAN Regional Forum (ARF) held in Hanoi, US Secretary of State Hillary Clinton said that the peaceful resolution of territorial disputes in the South China Sea is a "national interest" of the US, adding that "we oppose the use of threat of force by any claimant."

China has long-standing sovereignty disputes with countries including Vietnam, the Philippines, Indonesia and Malaysia over the Spratly and Paracel Islands. The Chinese Communist Party (CCP) administration has consistently insisted on "one-on-one" discussions with individual claimants while Asean wants negotiations to be held between China and the regional bloc as a whole. The region is the world's second-busiest international sea lane, with more than half the world's supertanker traffic passing through it.

Clinton voiced support for Asean's "international approach," saying that Washington backs a "collaborative diplomatic process" to resolve the territorial issue. Clinton also noted that the US has a national interest in "freedom of navigation, open access to Asia's maritime commons and respect for international law" in the region.

At least 12 of the 27 countries represented at the ARF Forum seconded Clinton's initiative, which seems to have caught China off guard. Chinese Foreign Minister Yang Jiechi said little other than reiterating that Beijing opposes the "internationalization" of the South China Sea issue.

Diplomatic analysts in Hanoi and Beijing said the US and Asean are increasingly concerned over Beijing's assertion of a kind of Monroe Doctrine over the South China Sea. (The Monroe Doctrine, introduced during the administration of US President James Monroe in 1823, states that any efforts by European powers to colonize land or interfere with sovereign states in the Americas would be met with force by the US.)

While individual countries, in particular the Philippines, had in the past indicated a willingness to hold bilateral talks with the Chinese over joint development of disputed islands in the Spratly chain, Asean members are now convinced that internationalizing the talks – possibly under American auspices – is the best way to safeguard their interests. Some confrontations have already taken place, including an incident in 2009 when Chinese naval vessels intercepted a US spy ship near a Chinese submarine base on Hainan Island. The US ultimately sent destroyers to escort the spy ship out of the area and no escalation took place.

Meanwhile, rivalry between China and the US has manifested itself on another front: Beijing's opposition to joint U.S.-South Korea sea-and-air military drills which started July 25. While the maneuvers were meant as a warning to Pyongyang, which is accused of torpedoing the South Korean warship Cheonan in late March, Beijing has fingered Washington for exacerbating its "anti-China containment policy."

This is despite the fact that due to China's intense opposition, the bulk of the exercises are being held in the Sea of Japan to the east of Korea, and not the Yellow Sea, which is wedged between China and South Korea. Earlier, Chinese Foreign Ministry spokesman Qin Gang indicated that Beijing "resolutely oppose(s) foreign military ships and planes coming to the Yellow Sea and other waters near China to engage in activities that affect China's security interests."

Official Chinese analysts have interpreted Washington's last-minute decision not to send state-of-the-art hardware such as the USS George Washington aircraft carrier into the Yellow Sea as a sign of America's reluctance to confront China. They argue that Beijing must do more to project its power in nearby oceans. Said Tang Xiaosong, a security expert at the Guangdong University of Foreign Languages and Foreign Trade: "Now that China has the prerequisites to be tough, we must seize the opportunity to play hard ball."

Major-General Luo Yuan, a professor at the Chinese Academy of Military Sciences and a popular commentator, has raised the specter of Washington taking advantage of the Korean crisis to perpetrate its anti-China encirclement policy.

"The US has never abandoned its containment policy against China," the general said. Luo noted that Washington had beefed up its "island chain" strategy – a reference to the American military boosting its capacities in bases ranging from Hawaii to Okinawa. "We must take forceful counter-active measures," Luo told the Chinese media.

It is understood that hard-line voices in the People's Liberation Army have been strengthened due to President Hu Jintao's decision to give the generals a bigger say in foreign and security policies.

Hu, who is focusing on preparations for the 18th Communist Party Congress set for 2012, requires the support of the top brass to ensure the large-scale promotion of members of his Communist Youth League Faction to senior slots at the pivotal conclave.