The last American combat brigade in Iraq has left the country, the US military has said.

美国军方称，伊拉克最后一支美国战斗旅已经离开。

The 4th Stryker Brigade, 2nd Infantry¹ Division began crossing by land into Kuwait in the early hours of Thursday, said a spokesman.

The US combat mission in Iraq is scheduled to end on 31 August.

But the Pentagon has not confirmed that the move by the 40,000 personnel from Stryker Brigade marks an early end to combat operations.

Most of them drove out of Iraq in a convoy²（护送，护卫） of armoured vehicles, say reports.

The journey along potentially hostile（敌对的，敌方的） desert roads had been carefully planned for weeks.

Some of the brigade remained behind to complete logistical and administrative³ tasks but would leave the country by air later in the day, the Associated Press reported.

The BBC's Jane O'Brien in Washington says the brigade（旅，队列） 's departure after seven and a half years is a significant step.

But the Pentagon has stressed that the official end to Operation Iraqi Freedom - the US military mission in the country - remains⁴ scheduled for the end of the month.

Some 56,000 US troops are set to remain in Iraq until the end of 2011 to advise Iraqi forces and protect US interests.

Those soldiers will be armed but will only use their weapons in self-defence or at the request of the Iraqi government.

State Department spokesman PJ Crowley said the US involvement in Iraq was far from over, but that it would be less intrusive⁵（侵入的，打扰的） and more civilian⁶ focused.

"We are ending the war ... but we are not ending our work in Iraq. We have a long-term commitment to Iraq," he told MSNBC.

Mr Crowley said the US had a trillion dollar investment to protect in the country and also wanted to see a significant return on the 4,415 troops who have lost their lives in the conflict.