The US protest to China this week over the alleged harassment of two of its naval ships by Chinese vessels, and China's reaffirmation of ownership of the contested Spratly Islands in the South China Sea, highlight two festering maritime disputes. Either could lead to conflict in the region unless carefully managed.
The tiff between Washington and Beijing resurrects a long-standing disagreement over the rights of coastal states in exclusive economic zones that extend for 370km from their shores, and the procedures to be followed by foreign military ships and planes when using waters and airspace in such zones.
The US says that the surveillance ship USNS Impeccable was about 120km south of Hainan Island on Sunday towing sonars, when it was forced to leave the area after Chinese vessels engaged in 'dangerous manoeuvres' nearby.
The Pentagon says that another US surveillance ship, USNS Victorious, was harassed last week in the Yellow Sea, 200km from China's coast.
Although the US has not signed the 1982 United Nations Convention on the Law of the Sea that regulates ocean use, it insists that its military ships and planes have freedom of navigation and overflight in 'international' waters, including exclusive economic zones of foreign states.
China, which has signed the law of the sea treaty, maintains that military operations, hydrographic surveys and intelligence collection by foreign ships or planes can only be carried out in such zones with permission from the coastal state. Some Asian countries take a similar view, even though they may be reluctant to challenge the US or other naval powers in the way China does.
China's military power is growing steadily, a fact underscored by last week's announcement that the Chinese defence budget will increase by nearly 15 per cent this year despite the economic slump. China's ambitions to become a naval power with global reach was also underlined by the recent deployment of Chinese warships on anti-piracy operations off Somalia, and the announcement that the Chinese Navy plans to build and operate aircraft carriers.