RUTHFULLY YOURS

By JEREMY PAGE

BEIJING—China’s first aircraft carrier began sea trials Wednesday, marking a milestone in the country’s rapid military modernization and long-term strategy to challenge U.S. military supremacy in Asia and project power far beyond Chinese shores.

The 300-meter-long carrier, based on an empty hull bought from Ukraine, sounded its horn three times as it ploughed through the morning fog around Dalian and headed out to sea, according to one witness writing on the military microblog of the state-run Xinhua news agency.

This undated photo shows China’s aircraft carrier anchored in Dalian, in northeast China.

The carrier, featuring its original ski-jump runway to launch fighters and a new engine and radar equipment, has been undergoing refurbishment for the past decade in the northeastern port.

Xinhua said the sea trials “would not take a long time,” without giving details of the exact duration or say what sort of tests would be carried out. “After returning from the sea trial, the aircraft carrier will continue refit and test work,” it said.

The provincial Maritime Safety Authority said on its web site that “all vessels will be barred from entering” a small section of sea off Dalian until 6 p.m. local time Aug. 14.

The launch had long been expected as final preparations of the vessel—which has yet to be named by China—were visible from many points around Dalian and had been regularly photographed and documented online by amateur enthusiasts.

A Chinese company purchased the empty hull of a carrier called the Varyag from Ukraine in 1998 on the understanding that it would be used as a floating casino, but it was later towed to Dalian via the Black Sea, the Mediterranean and the Straits of Malacca.

China officially acknowledged only last month that it was refurbishing the vessel, and tried to ease regional concerns by saying it would be used for “research, experiments and training” and would take a long time to become fully operational.

China is the only one of the five permanent members of the U.N. Security Council, which includes the U.S., Britain, France and Russia, without an operational carrier. India and Thailand have a carrier each, while Japan has one that carries helicopters.

The launch is nonetheless likely to fuel fears about China’s growing naval and air power among U.S. and Asian military officials, many of whom say Beijing has been taking a more assertive stance on territorial disputes around its waters in the past two years.

China has had run-ins this year with Vietnam and the Philippines over disputed waters in the South China Sea, where Taiwan, Malaysia and Brunei also have claims. It has clashed repeatedly with Tokyo over disputed islands in the East China Sea.

Tensions also have been mounting between the U.S. and China, which demanded last month that the U.S. stop naval and aerial reconnaissance flights around Chinese waters, and reject a request for new F-16 fighter jets from Taiwan, which Beijing sees as a rebel province.

Chinese military experts have made it clear that their armed forces aren’t intent on matching U.S. military might—or confronting the world’s only superpower. Rather, they are developing the capability to enforce China’s territorial claims, protect its economic interests far from its shores and hinder access to Asian waters by U.S. forces in the event of conflict.

U.S. officials and experts say it will take China many years to develop a fully operational carrier group, complete with deck-borne fighter jets, and decades, if ever, to match the U.S. Navy’s current capabilities.

Some see the vessel’s launch as more of a symbolic step in China’s long quest to develop its own carrier—an idea first proposed by the nationalist naval commander Chen Shaokuan in 1929 and revived by Admiral Liu Huaqing in the 1970s.

Both Chinese and foreign military experts say the carrier has limited combat potential on its own, and will be used mainly to test equipment and train personnel, especially pilots who must learn to take off and land aircraft on a moving deck.

But it could be used for limited patrols around China’s territorial waters, as well as conducting visits to foreign countries to try to enhance military relations and help them grow accustomed to China’s newfound naval strength.

It will also provide China with crucial experience for designing, building and operating indigenous carriers, the first of which some defense experts say is already under construction at a shipyard in Shanghai and could be launched by 2015.

Most experts say that at least three carriers are required to be effective, so that one can be in theater, one in transit and one in port for repairs and resupplies. Each requires its own carrier group, which would include several other vessels.

“China’s ‘starter carrier’ is of very limited military utility, and will primarily serve to confer prestige on a rising great power, help the military master basic procedures, and to project a bit of power,” wrote Andrew Erickson, an associate professor in the U.S. Naval War College’s Strategic Research Department, in a research note.

“The carrier’s maiden voyage appears to be a show cruise conducted close to home to both make the vessel a bit less accessible to prying eyes (and unauthorized digital cameras) and also keep it near its home port if any mechanical problems materialize.”

Write to Jeremy Page at jeremy.page@wsj.com