President Bush today asked the American people and Congress to show patience with a war which opinion polls suggest is now even more unpopular in the United States than it is in Iraq.

Speaking on the day that the war in Iraq entered its fifth year, Mr Bush acknowledged it was “tempting to look at the challenges” and decide “to pack up and go home”.

In remarks addressed directly to Democrats on Capitol Hill, he said while such a plan “might be satisfying in the the short run” the long term consequences would be devastating.

“If American forces were to step back from Baghdad before it is more secure, a contagion of violence could spill out across the entire country.

“In time, this violence could engulf the region. The terrorists could emerge from the chaos with a safe haven in Iraq to replace the one they had in Afghanistan, which they used to plan the attacks of September the 11th, 2001. For the safety of the American people, we cannot allow this to happen.”

The fourth anniversary of the invasion was marked by publication of new polling evidence from both Iraq and the US which showed backing for the war falling to ever lower levels in both countries.

An Opinion Research survey for CNN suggested that support among US voters had dropped from 72 per cent in 2003 to 32 per cent with more than six in ten Americans now saying Iraq was not worth fighting for.

A separate BBC/ABC poll conducted by D3 Systems indicated that 47 per cent of Iraqis still believed the US-led invasion was “absolutely” or “somewhat” right, while 63 per cent said American and British troops should only go home after security has been improved - even though fewer than one in five expressed confidence in them.

The survey showed that Iraqis are becoming increasingly pessimistic with less than 40 per cent saying life was good, compared to 71 per cent two years ago. It painted a picture of a society increasingly polarised on ethnic lines with Iraq, with Sunnis markedly less optimistic than the majority Shia population.

Mr Bush, in his televised statement from the White House Roosevelt Room, said his strategy of sending in around 30,000 additional US troops to secure Baghdad and Iraq’s troubled Anbar Province “will need more time to take effect... there will be good days and bad days ahead as the security plan unfolds.”

The president, who has repeatedly predicted that America “will prevail” in the war, used noticeably more conditional and even hypothetical language to describe the prospect of victory. “Four years after this war began, the fight is difficult, but it can be won. It will be won if we have the courage and resolve to see it through,” he said.

Democrats in the House of Representatives are this week seeking to attach conditions to a $124 billion war funding Bill which would force the withdrawal of US combat troops from Iraq by the autumn of next year at the latest. They have also, much to the anger of the White House, inserted around $30 billion of spending on unrelated funding for domestic programmes.

Mr Bush has promised to veto any legislation setting a timeliness for withdrawal, saying yesterday that the progress Iraq’s leaders are making should be matched by “important commitments of our own”.

He added: “Members of Congress are now considering an emergency war spending bill. They have a responsibility to ensure that this bill provides the funds and the flexibility that our troops need to accomplish their mission.

“They have a responsibility to pass a clean bill that does not use funding for our troops as leverage to get special-interest spending for their districts. And they have a responsibility to get this bill to my desk without strings and without delay.”

FACT BOX:

Cost of Iraq War since 2003, including pending funding Bills: almost $500 billion.

Confirmed US deaths: 3,210

British deaths: 124

Iraqi civilian deaths: 68,000 (estimated)

Sources: US Department of Defence, AP, ICasulaties.org

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