Staff Sergeant Tyrone L. Hadnott is sentenced to four years in prison, Kyodo says.

Four other charges, including rape of a child under 16, making a false official statement, adultery and 'kidnapping through inveigling', or trickery, were dropped in a plea bargain, according to Kyodo.

Japan hosts some 50,000 American troops under a security treaty.

About half of them are based on the tiny, congested island of Okinawa. -- AP