'I only have one thing to express and that is our true anger,' said Chief Cabinet Secretary Nobutaka Machimura, the top government spokesman, on Monday.

Corporal Shawn Cody Jake, 21, was found at around 4.25am on Monday on a sofa inside the house of a local family in Nago city who did not know the man, according to the Okinawa police.

'He was arrested at the scene for trespassing,' a police spokesman said.

The arrest came only a week after another Marine was arrested for allegedly sexually assaulting a 14-year-old girl also on Okinawa, which hosts half of the more than 40,000 US troops in Japan.

Top US officials last week flew to Okinawa to offer personal apologies for the alleged rape and promised to tighten discipline among US troops.

Mr Machimura urged Washington to do more and said the government would bring up the issue when US Secretary of State Condoleezza Rice visits next week.

'They are not showing a sense of discipline,' Mr Machimura said.

'We are expecting a visit by Secretary of State Rice next week. We must urge the US government to strongly regret' the conduct of its soldiers, he said.

The United States stations troops in Japan under a security treaty with its key Asian ally, which has been officially pacifist since World War II.

Mr Machimura feared the latest incidents may affect ongoing moves to shift US troops within Japan, although he doubted they would halt the plan entirely.

'We don't believe (the plan) will be affected. But we must review the situation to see if there are any effects,' he said.

Last week's incident rekindled memories of the gang-rape in 1995 of a 12-year-old girl by three US servicemen, which set off major protests on the island and set in motion a process to reduce the number of US troops there. -- AFP