The killing of a woman near a U.S. naval base in Japan could complicate efforts by Washington and Tokyo to win Japanese public support for a realignment of American military forces in the country. A U.S. sailor is suspected of killing the woman. The sailor is being held by the Navy and Japanese officials are expected to eventually take him into custody.

A sailor from the U.S.S. Kitty Hawk aircraft carrier is suspected in the death of a 56-year-old Japanese woman earlier this week.

Japanese police say Yoshie Sato was beaten during an apparent robbery and died of internal bleeding.

U.S. Embassy officials on Friday called the death senseless and said they were working with Japanese and Navy authorities to make sure that "justice is done" in the case.

The Navy will not release the name of the suspect unless he is charged, but he has been described as a sailor in his 20s assigned to the aircraft carrier, which is based at Yokosuka, near Tokyo.

In a statement issued Friday, the commander of U.S. Naval Forces Japan, Rear Admiral James Kelly, apologized for the death and ordered a four-day midnight curfew.

Navy spokesman Jon Nylander says that is to give personnel a chance to reflect on how to improve relations with the civilian community and to demonstrate remorse for the death.

"All sailors, dependents, civilian workers, everybody attached to the Navy in Japan will be in their homes," he said. "And the idea is that they reflect on this event and the tragedy and consider what they need to do personally to strengthen the relationship and consider the loss that the family has suffered."

Japanese media say the sailor has confessed to the killing and that U.S. authorities on Friday agreed to allow Japanese police to question him.

Navy Commander John Wallach says U.S. military authorities and Japanese police are jointly investigating. But he did not confirm whether an agreement has been reached allowing Japanese detectives to question the sailor.

"One issue is the issue of custody where they would actually request to take the sailor into their custody. That request has not been received yet," Commander Wallach said. " The second issue is a request to question the sailor while he is in U.S. Navy custody, in confinement. I'm not going to comment on anything regarding the investigation right now, but I just wanted to distinguish between those two possible requests."

Crimes committed by U.S. troops in Japan are politically sensitive and usually generate a public backlash against the bases. This latest incident could strengthen opposition to plans to realign the U.S. forces in the country.

Japanese and U.S. officials are trying to win support to base, for the first time, an American nuclear-powered aircraft carrier at Yokosuka, and to build a new military airstrip on the southern island of Okinawa.

There are about 50,000 U.S. troops in Japan. Last October, the United States agreed to transfer 7,000 Marines out of Okinawa and to move other personnel within the country. The deal also includes sending 800 troops from the United States to an Army base near Tokyo - which many local residents oppose.

Japan's Foreign Ministry says talks are to be held next week in Washington over the force realignment.