AL-ASAD AIR BASE, Iraq (AFP) - U.S. President George W Bush paid a surprise visit to Iraq on Monday, just days before a crucial report to Congress on Washington's strategy in the war-torn nation.

The trip coincided with the withdrawal of British troops from their last base in the southern Iraqi city of Basra amid tensions between Washington and its top ally Britain over their policy in Iraq.
""This is the last big gathering of the president's military advisors and the Iraqi leadership before the president decides on the way forward,"" said Geoff Morrell, a Pentagon spokesman.
The White House is to make a formal report to Congress on September 15 aimed at convincing U.S. lawmakers to continue funding the Iraq war, four and a half bloody years since the U.S.-led invasion of 2003.
Bush, whose itinerary was not immediately known, arrived a the desert air base of Al-Asad in the restive western province of Anbar along with Secretary of State Condoleezza Rice, national security adviser Stephen Hadley, and other senior aides.
Waiting for him were U.S. Defense Secretary Robert Gates, General Peter Pace, the chairman of the Joint Chiefs of Staff, Admiral William Fallon, the commander of U.S. forces in the Middle East, and General David Petraeus, the top U.S. commander in Iraq.
It was Bush's first visit to Iraq since June 2006, which followed the killing by U.S. forces of the then leader of Al-Qaeda in Iraq, Abu Musab al-Zarqawi.
Opposition Democrats who control the House of Representatives and Senate have been pushing for months to force a deadline for U.S. troops to leave Iraq.
But Bush and his generals have argued for time to make the so-called troop ""surge"" work after the U.S. military deployed tens of thousands of extra troops in February to try to end the violence in Iraq.
Bush's visit came just hours after British forces slipped out of their last base in the Iraqi oil port of Basra under cover of darkness and handed over control of the base to their Iraqi comrades, leaving behind a city in the grip of a brutal militia turf war.
""The operation to leave the Basra Palace has now been completed successfully,"" British defense ministry spokesman told AFP, adding that it involved some 500 soldiers.
Iraqi soldiers were seen hoisting the Iraqi flag and posting guards outside the palace complex and General Mohan Farhad, commander of Basra military operations, said it would remain under Iraqi military control until Prime Minister Nuri al-Maliki decides its fate.
""The Iraqi army has now taken over responsibility and the area is off-limits. No one can approach except those who are authorised,"" he told AFP.
Retired Major General Tim Cross, the top British officer involved in planning post-war Iraq, hit back, saying he had raised serious concerns with then U.S. defense secretary Donald Rumsfeld about the risk of the country descending into chaos.
But Rumsfeld ""ignored"" or ""dismissed"" his warnings, Cross told the Sunday Mirror.
On Saturday, General Sir Mike Jackson, the head of the British army during the invasion, also launched a fierce attack on Washington over its handling of troubled Iraq since then.
He branded U.S. post-invasion policy ""intellectually bankrupt"" and said Rumsfeld was ""one of the most responsible for the current situation in Iraq.""
There are about 5,500 British troops in Iraq, most of whom are based in and around Basra, though that number is set to drop to around 5,000 by the end of the year.
The British troops leave behind a city in the grip of a brutal turf war between rival militias, and many policy experts now warn of more chaos ahead.
Almost 160 British soldiers have been killed in Iraq since the invasion