A U.S. envoy expressed "great regret" on Thursday over the suspected rape of a 14-year-old girl by a U.S. Marine in Okinawa, southern Japan, as both Washington and Tokyo try to keep the incident from hurting broader ties.

The arrest last week of the 38-year-old Marine, Tyrone Hadnott, has rekindled memories of the rape of a 12-year-old girl in Okinawa in 1995, which sparked huge protests against the U.S. bases there and raised concerns about damage to the security relationship.

Hadnott denied rape but admitted forcing her to kiss him, police have said.

U.S. Assistant Secretary of State Christopher Hill spoke with a senior Japanese foreign ministry official about the issue ahead of a visit to Tokyo by U.S. Secretary of State Condoleezza Rice next week, during which she is expected to face complaints about military discipline.

In events further angering Okinawa residents, two Marines were arrested on the southern Japan island at the weekend, one accused of trespassing and the other of drink driving.

The U.S. military on Wednesday slapped a 24-hour curfew on troops on the island that bans them from leaving their homes or bases except to go to school, to worship or visit a doctor. "I expressed my great regret of the situation that has developed in Okinawa, my great concern about the feelings of the people of Okinawa and the fact that this is a very difficult time," Hill told reporters after talks with Shinichi Nishimiya, director general of the ministry's North American affairs bureau.

Kyodo news also reported on Thursday that the U.S. military took an army member into custody earlier this month for an alleged sexual assault on a Philippine woman in Okinawa.

A U.S. military spokesman said in an e-mail that it had received reports that a Philippine woman, 21, who was staying in an Okinawa City hotel with a U.S. service member, was taken to hospital for an injury, and that police were investigating.

Prime Minister Yasuo Fukuda on Monday said he would discuss ways to prevent a recurrence of the recent incidents in Okinawa with Rice during her visit.

Okinawa plays host to the bulk of the 50,000 or so U.S. troops based in Japan. Local residents often complain about the noise, crime and pollution associated with the bases.