U.S. Navy bases across Japan were busy Wednesday as the United States prepares to retaliate for last week's terrorist attacks in New York and Washington.

The 8,422-ton guided-missile destroyer Curtis Wilbur returned to Yokosuka naval base in Kanagawa Prefecture after departing Monday on an undisclosed mission.

U.S. Navy officials declined to comment on the warship's earlier departure, which was followed by the 9,407-ton missile cruiser Vincennes. Both vessels are equipped to carry Tomahawk cruise missiles as well as antiaircraft missiles and antisubmarine weapons.

However, it is believed the two warships conducted drills with the U.S. Navy's nuclear-powered submarine Bremerton, which surfaced later Monday in waters near the base. The 6,080-ton submarine anchored for about an hour before setting out to sea again.

The Foreign Ministry said Wednesday the Bremerton, with some 310 crew on board, will enter Sasebo port in Nagasaki Prefecture at around 10 a.m. today.

It will stop at the port for rest and refueling, ministry officials said, citing a prior notice sent by the navy. The submarine's departure remains undecided, they added. It will be the Bremerton's first visit to the port since the terrorist attacks.

Memorial event planned

A memorial service for the victims of last week's terrorist attacks in the United States will be held Sunday in Tokyo, the government announced Wednesday.

The event, to be hosted jointly by America-Japan Society Inc. and the Japanese government, will take place at Tokyo Big Sight in Koto Ward from 2 to 3 p.m.

Prime Minister Junichiro Koizumi is scheduled to attend, Chief Cabinet Secretary Yasuo Fukuda told a regular news conference.

"This memorial service will be held to mourn for all the people who lost their lives, express our most sincere sympathy for their families and pray those still missing will be found safe and sound," Fukuda said.

The event is open to the public.