The presence of US military bases in Japan dates from the end of World War II, when US forces under General Douglas McArthur occupied the country following the dropping of American atomic bombs on Hiroshima and Nagasaki.

The shattered country remained under US administration until 1952, when it regained its independence under a constitution which restricted its military activities to "self-defence."

The previous year, in September 1951, Japan, the United States and 46 other states had signed the Treaty of San Francisco, which stipulated that US forces were to remain based in the country.

The US still has a total of 86 military facilities scattered around Japan, with many in the region of the capital Tokyo.

More than half of the 47,000 US military personnel still stationed in Japan are based on the island of Okinawa, where their presence has been an irritant to relations in recent years.

In May 2006 the two countries reached an agreement on moving some of the US forces on Okinawa to the island of Guam, which is ruled by the United States.

The agreement would see 8,000 US troops and their dependents leave the island by 2014, and allow Japan to resume control of a total of five military facilities.

Opposition to the US bases on Okinawa has simmered for decades, with locals complaining about aircraft noise, pollution, the risk of accidents and crimes committed by servicemen, especially the gang-rape of a schoolgirl in 2005.