Vietnam’s Foreign Ministry accused China of exacerbating tension in the South China Sea earlier this week after a confrontation between a Vietnamese oil and gas survey vessel and Chinese patrol boats took place some six hundred kilometers south of Hainan island.

Vietnam claimed that the Chinese ships had deliberately cut a submerged cable towed by the Vietnamese vessel. China denied the allegation and blamed its southern neighbor for causing the incident, saying that its oil and gas operations “undermined China’s interests and jurisdictional rights.”

Although the two East Asian countries are among the few remaining communist states in the world, their bilateral relations haven’t much improved since the brief Sino-Vietnamese War of 1979. Border disputes and regional rivalry continue to be cause for mutual mistrust.

Vietnamese relations with the United States by contrast have been improving rapidly. The two held naval exercises together and when Secretary of State Hillary Clinton attended a South East Asian cooperation summit in Hanoi last summer, she professed that the United States have a “national interest” in mediating disputes between China and its neighbors.

China’s revisionist maritime border stance in Southeast Asia is mainly responsible for a series of disputes in recent years. This body of water, through which passes a third of all commercial maritime traffic worldwide and half of the hydrocarbons destined for Japan, the Korean Peninsula and northeast China, is of great strategic importance to the Chinese but similarly vital to continental Asian nations as Vietnam.

The issue involves some two hundred islands and coral outcroppings which are claimed by Brunei, China, Indonesia, Malaysia, the Philippines, Taiwan and Vietnam. China has always insisted that its exclusive economic zone extends far into the South China Sea and claims all islands as its territory. Other countries in the region have eyed the United States to defend their claims.

The Americans maintain a strong military presence in the Pacific with bases in Japan, Korea and Taiwan. China has complained about this American shadow over the South China Sea and interpreted Clinton’s remark in Hanoi last year as an “attack”. As the Chinese foreign minister put it, “China is a big country and other countries are small countries and that is just a fact.”