BEIJING?China has dispatched its most modern patrol ship to the South China Sea, state press said, after an incident with a US naval vessel and a fresh claim by the Philippines to the disputed territory.

The Beijing News said the vessel would conduct patrols of what it called China?s exclusive maritime zone in the disputed waters surrounding the Paracel and Spratly Islands.

It said the converted naval rescue ship would aid Chinese fishing boats and transport vessels.

Beijing sent the patrol ship after the United States decided to send heavily armed destroyers, including the USS Chung-Hoon, to escort US surveillance ships operating in the South China Sea after a tense naval standoff last week.

The US claims the Navy mapping ship Impeccable was operating legally when it was harassed by Chinese boats in international waters about 120 kilometers off China?s southern island province of Hainan. China?s foreign ministry has said the US claim isn?t true.

US officials say the Impeccable was on a mission to seek out threats such as submarines and was towing a sonar apparatus that scans and listens for submarines, mines and torpedos. With its numerous Chinese military installations, Hainan offers rich hunting for such surveillance.

Of particular interest is the new submarine base near the resort city of Sanya that is home to the Chinese navy?s most sophisticated craft.

Photographs of the base taken last year and posted on the Internet by the Federation of American Scientists show a submarine cave entrance and a pier, with a Chinese nuclear-powered Jin class sub docked there.

While little else is known, its location on the South China Sea offers the Chinese navy access to crucial waterways through which much of the shipping bound for Japan and Northeast Asia must travel.

Neither Beijing nor Washington has yielded in their conflicting versions of events?indicating neither side was prepared to back down, even as they prepare for a much-anticipated first meeting between China President Hu Jintao and President Barack Obama at next month?s G20 summit in London.

China?s claim to the entire South China Sea and its hundreds of islands and reefs overlaps with those of a half-dozen other nations, leading to occasional clashes and standoffs. Increasingly, China?s rapid naval upgrade, exemplified by the Hainan base, is putting muscle behind its arguments.

From Russia, China has purchased a dozen Kilo-class diesel submarines, Sovremmenny class destroyers and supersonic Sunburn and Sizzler anti-ship missiles. China?s own advanced Shang, Song and Yuan class submarines are being produced at a rapid tick, and there is increasing talk of an aircraft carrier being launched in coming years.

China?s territorial claims are sharpened still more by Beijing?s interpretation of the United Nations Convention on the Law of the Sea. China sees the convention as giving it the right to ban a broad range of activities within its exclusive economic zone. That grates against the US position that the navy ships were in international waters and therefore had the right to conduct surveying. AP and AFP