Some 1,500 US sailors and Marines and 1,700 Thais are participating in the annual Cooperation Afloat Readiness Training, or CARAT, exercises. A US envoy said the exercises are aimed at boosting security in Southeast Asia.

"CARAT, now in its ninth year, is the most important naval exercise between our two countries," US charge d'affaires Ravic Huso said at Chuck Samet naval base on Thailand's central coast, according to an official text of his speech at the opening ceremony.

"The goals of this exercise are clear: to give our navies the opportunity to train together, to enhance our naval operational readiness, and to prepare us to work together to meet real world maritime challenges and to ensure regional stability and security."

The annual exercises, which have similar phases in Brunei, Singapore and Malaysia, will involve at least nine frigates and seven aircraft from the Royal Thai Navy, a naval spokesman said.

The US task force of at least four ships is led by the guided missile cruiser USS Vincennes, the US embassy said.

Training is scheduled in areas such as manouvering and communications, gunnery, diving and salvage, and amphibious operations.

US troops last week wrapped up Cobra Gold, their biggest Asian war games of the year, after two weeks of manoeuvres with Thai and Singaporean forces in Thailand which focused in part on dealing with terrorist threats.

"We have been engaged in the global war on terrorism in Afghanistan but also in the Asia-Pacific region," Huso said Friday.

He stressed that joint naval operations help reinforce a "collective will" to promote maritime security in Southeast Asia.

The region contains some of the world's most strategic shipping lanes, including the Malacca Straits between Malaysia and Indonesia which carries one third of the world's trade but remains vulnerable to attacks from pirates and terrorist groups.

WAR.WIRE