TOKYO  An American marine accused of raping a 14-year-old girl on Okinawa was released by the Japanese police on Friday after the girl dropped her accusation, the police said.

It was unclear if the marine’s release could help defuse the furor in Japan over the case, which had led to wide questioning of the military alliance with the United States and the presence of more than 40,000 American troops here. Fallout from the accusation prompted Secretary of State Condoleezza Rice to express deep regret to the Japanese prime minister, Yasuo Fukuda, on Wednesday.

Earlier, Mr. Fukuda had called the episode “unforgivable” and demanded that the United States take action to prevent crimes by its service members.

The marine’s arrest on Feb. 11 incited protests on Okinawa, where there are raw memories of a 1995 rape of a 12-year-old girl by three American servicemen.