America currently has some 150,000 troops in Iraq

A US military pullout now, he said, would "hand Iraq over to enemies".

He said Iraq's election was the start of constitutional democracy at the heart of the Middle East.

"This vote, 6,000 miles away, in a vital region of the world, means that America has an ally of growing strength in the fight against terror," said Mr Bush.

More than 2,100 US troops have been killed in Iraq since the end of the US-led invasion of April 2003, as well as more than 30,000 Iraqis.

'Noble and necessary'

Speaking from the Oval Office, Mr Bush appealed to Americans to be patient in a "difficult, noble and necessary cause" and not be swayed by "defeatists who refuse to see that anything is right".

Being your president requires doing what I believe is right and accepting the consequences George W Bush US president

"The war is difficult - it does not mean that we are losing," he added.

Mr Bush insisted the war had helped stave off new terror attacks on the US since 9/11.

Terrorists in Iraq, he said, felt a "tightening noose and fear the rise of a democratic Iraq".

"I know that some of my decisions have led to terrible loss and not one of those decisions has been taken lightly," he added.

"I know that this war is controversial, yet being your president requires doing what I believe is right and accepting the consequences."

The BBC's James Coomarasamy reports from Washington that this is Mr Bush's fifth speech on Iraq in under three weeks.

In tone, he is more contrite than he has been in the past, more willing to admit mistakes and listen to what he calls his honest critics, but no less determined to stay the course, our correspondent says.

Cheney in Iraq

US Vice-President Dick Cheney made an unannounced visit to Iraq on Sunday - his first since the 2003 invasion.

Mr Cheney praised Iraq's "tremendous" elections during his visit.

It was kept so secret that it is thought even the Iraqi prime minister was not told beforehand.

As one of the main advocates of the Iraq war, Mr Cheney has come under constant criticism by opponents.

The vice-president flew around the Baghdad area in a pack of eight fast-moving Blackhawk helicopters with guns mounted on the sides, the Associated Press news agency reports.

He had talks with Prime Minister Ibrahim Jaafari and Iraq's President Jalal Talabani before meeting US commanders.

Last month, Mr Cheney strongly denied allegations that the Bush administration had purposely misled the American people on pre-war intelligence.

"The president and I cannot prevent certain politicians from losing their memory, or their backbone - but we're not going to sit by and let them rewrite history," he said.

Most recently the US vice-president has been accused of sanctioning the abuse of prisoners by US troops.