THE US NAVY'S announcement last week that three Los Angeles-class attack submarines will be stationed on Guam slipped by without much fanfare in the regional media, but alarm bells must be ringing in Beijing. When the USS City of Corpus Christi arrives at its new base later this month, it will mark the first time a nuclear-powered attack submarine has had a home port on the Pacific island, which is strategically located midway between Hawaii and the Philippines. When the other boats - the USS San Francisco and another yet to be announced - arrive later this year they will be an irritating thorn in the side of China's military planners. As China improves its capabilities with modern fighter jets, ships and submarines, the US is trying to stay one step ahead by boosting its presence in the Pacific and selling arms to Taiwan. The Americans have made no secret of the fact the subs are being sent deeper into the Pacific to remind Beijing of who rules the ocean. 'The US is sending China a message, and the message is that the US navy is the most powerful navy in the Pacific and it intends to stay that way,' said Phillip Saunders, director of the East Asia Nonproliferation Programme at the Monterey Institute of International Studies in California. Mr Saunders said the likely reason China had not complained bitterly about the move was the desire for good relations leading up to President Jiang Zemin's visit to the US later this month. Beijing has reason to be upset at the prospect of having the warships closer to China's coastline. The submarines are among the most sophisticated and versatile weapons in the US arsenal. Along with torpedoes, they can carry Harpoon anti-ship missiles and Tomahawk cruise missiles to attack sea and land targets. The subs also can fire a version of the Tomahawk that has a range of 2,500km and carries a nuclear warhead. The submarines are extremely hard to detect and their nuclear propulsion system allows them to cruise underwater for weeks at a time, stalking ships and other submarines or gathering intelligence. Using the subs as unseen spies will be of particular interest to the US in the aftermath of the April 2001 EP-3E incident, in which a US navy surveillance plane and a Chinese fighter collided, killing the Chinese pilot. The USS City of Corpus Christi has just had a US$300 million (HK$2.33 billion) refit that saw it equipped with the latest combat systems and sensors. Mr Saunders said China did not have the technology or anti-submarine warfare expertise to locate and track modern submarines effectively. Jane's defence analysts have come to the same conclusion, warning that even the People's Liberation Army's most modern ships 'lack a credible undersea warfare capability'. US defence officials told Reuters the submarine shift was in line with a Pentagon push to give the military a more visible presence in the Asia-Pacific region. 'We lost key air and naval bases in the Philippines several years ago and have been looking for ways to reclaim some of that presence,' one said. Since the end of the Cold War, the US Pacific submarine force has shrunk from 40 attack submarines to 25. US navy officials said the redeployment of the submarines would double the amount of time they were available for missions because they would no longer have to travel from Pearl Harbour, Hawaii, or the continental US to reach patrol areas in the western Pacific. Other branches of the US military are considering their own show of strength on Guam. Citing concerns over China, General William Begert, who commands the US air force in the Pacific, is pushing to have advanced F-22 fighters, bombers and support aircraft moved to the island. Guam was a base for B-52 bombers during the Vietnam War, but no aircraft are based there at the moment. Analysts say the US military build-up is in line with the security doctrine outlined by President George W. Bush last month. Mr Bush said the US would not accept any challenge to its military supremacy, and singled out China's attempts to modernise the PLA as a concern. China has invested heavily in recent years to give its navy a blue water capability - ships that can operate in battle groups far out into the ocean. Purchases have included four Russian Sovremennyy class destroyers, two of which are in service, and up to eight Kilo-class submarines to be delivered by the end of 2007. Media reports put the value of the deals at US$2.4 billion. But most of the PLA's fleet is still made up of coastal patrol ships that are hopelessly obsolete. China has no aircraft carriers and domestic submarine development programmes have been plagued with technical problems. While the prospect of a war between the two powers is remote, the arrival of the US submarines on Guam serves as an irritating reminder to Beijing of China's military shortcomings. It also sends the message that the Americans intend to stay more than a few steps ahead of China in any future arms race. Doug Nairne is the Post's deputy China editor