President Bush effectively hands the Iraq war to his successor today during a speech in which he is expected to sign off on his top commander's plan for an indefinite halt of American troop withdrawals.

Responding to two days of testimony on Capitol Hill by General David Petraeus, Mr Bush will largely embrace his advice that the security situation in Iraq is still so precarious that a massive US troop presence is required for the foreseeable future.

General Petraeus, who called security gains “fragile and reversible”, called for a halt to withdrawals in July after troop levels had been reduced to about 140,000 —- the same number deployed in Iraq before last year's “surge” of 30,000 extra personnel.

It takes at least two months to remove a combat brigade once the order has been given. General Petraeus's plan means that no significant troop reductions will occur before the election in November, with the likelihood of at least 130,000 troops in Iraq when the next president takes office in January.

Previewing Mr Bush's speech, Dana Perino, his spokeswoman, left little doubt that Mr Bush will back his battlefield commander and is very unlikely to be swayed by a meeting with congressional leaders before he speaks.

In view of “the President's practice of listening to his commanders on the ground, it would not be to type if he did not listen to them”, Ms Perino said.

She added: “I think he's pretty far down the path of what he's going to say tomorrow. What the President is looking to do is to make sure that he makes tough decisions now that can help make for a smooth transition when the next president takes over.”

On his second day of testimony —- the fifth anniversary of the fall of Baghdad —- General Petraeus was asked again about the botched assault by Iraqi government forces on Shia militia in the southern city of Basra two weeks ago.

General Petraeus, who said in testimony to a Senate committee on Tuesday that the operation had been poorly planned and badly executed, conceded that the Iraqi Prime Minister, Nouri al-Maliki, had ordered the assault too quickly and against his advice.

Speaking to the House Armed Services Committee, General Petraeus was asked about the 1,500 Iraqi personnel who, in effect, fled the battle scene.

He said that a majority of them had been police, who were easily intimidated by local militia, and that a new army unit, fresh from training, had not been up to the task. He said that most of the Iraqi forces stayed in the fight.

Four months after the British handed over control of Basra, General Petraeus said that there were militia strongholds controlling “very densely packed neighbourhoods” and that a military solution was unlikely because an assault could cause “untold damage”.

On the progress made by Iraqi forces generally —- key to further US withdrawals —- General Petraeus described it as a “very, very mixed bag across the board”. He graded the reliability of the Iraqi Army in the “B-minus/B range, with recognition that there's a lot of work needed to be done”.

General Petraeus's testimony, and the reality of a now five-year war that has no end in sight, produced a sobering two days and exasperation from Democrats and an increasing number of Republicans.

Yet Mr Bush still has enough votes in the Senate to prosecute the war as he wishes, enabling him to hand over a huge troop presence to his successor.

Hillary Clinton, campaigning in Pennsylvania for the April 22 primary, said: “I call on President Bush to answer the question General Petraeus did not: what is our endgame in Iraq given the failure of the surge to achieve [political reconciliation]?”

Barack Obama suggested that US ambitions in Iraq should be to accept “a messy, sloppy status quo” rather than staying there for years to come.

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