A US destroyer equipped with missile track systems has started patrolling the Sea of Japan as part of a missile defense system, US Navy Secretary Gordon England said in Washington Friday.

The USS Curtis Wilbur, one of three ships in the US 7th Fleet tasked with the patrols, left its base just south of Tokyo earlierthis week as scheduled, England told reporters at the Pentagon.

"We do have our Aegis destroyers deployed and indeed they do have tracking capability as we committed to do before the end of the year," England said.

The deployment of the destroyer is part of a missile defense system President George W. Bush ordered to deploy to protect the United States from ballistic missile attacks.

The destroyer will track missile activity in the region and transmit data to Fort Greely in Alaska and Vandenberg Air Force Base in California, two main bases for the ground-based missile defense system.

The Pentagon has deployed five interceptor missiles at Fort Greely and another is set to be placed there later this month. Twomore are set to be installed at Vandenberg next month, officials at Pentagon's Missile Defense Agency (MDA) said.

Pentagon officials said the United States is on target to declare the system's "initial defensive capability" this year, providing a limited defense against long range missile attacks.

Critics accuse the Bush administration of playing politics by rushing to deploy a system not sufficiently tested in the electionyear. The Pentagon has not conducted any flight tests since December 2002 when the system failed to intercept a mock enemy missile in a test.

The Pentagon's chief weapons evaluator has calculated that the system may be capable of hitting its targets only about 20 percentof the time. But the MDA, which is responsible for developing the system, offers estimates of greater than 80 percent.

Source: Xinhua