President George W. Bush is likely to accept recommendations for a pause in the drawdown of US troops from Iraq when the current round of withdrawals ends in July.

The White House said Mr Bush saw “some merit” in proposals to assess the impact of the first drawdown before making further reductions in US troop numbers.

The deliberations came after the number of US soldiers killed in Iraq reached 4,000 on Sunday, prompting fresh calls from Democrats for an end to the war.

General David Petraeus, the US commander in Iraq, and Ryan Crocker, the US ambassador in Baghdad, are expected to recommend a pause in troop withdrawals in their next progress report to Congress next month.

They have signalled that a period of consolidation is needed after US troop numbers reach 140,000 in July, down from 170,000 when the drawdown was announced last September.

About 12,000 troops have so far returned home without replacement.

The rate of US deaths in Iraq has slowed sharply since last year’s “surge” in troop numbers, but a recent spike in violence has raised concerns that security gains could be squandered if the drawdown is too hasty.

Mr Bush was scheduled to hold a video conference with Gen Petraeus and Mr Crocker on Monday. The White House said he was close to making a firm decision.

The 4,000th US military death came when four soldiers were killed by a roadside bomb in Baghdad on Sunday, less than a week after the fifth anniversary of the invasion. At least 97 per cent of the casualties have occurred after Mr Bush declared an end to “major combat” operations in Iraq on May 1 2003.

Gen Petraeus told the BBC on Monday he had evidence that Iran was behind Sunday’s bombardment of Baghdad’s heavily fortified Green Zone. He thought Tehran had trained, equipped and funded insurgents who fired mortars and rockets.

Dana Perino, White House press secretary, said the president had “grieved for every lost American life”.

“He bears the responsibility for the decisions he made and he also bears the responsibility to continue to focus on succeeding,” she said.

Barack Obama, the Democratic presidential hopeful, said the 4,000th death brought a reminder of the urgent need to end the war. “It is past time to end this war that should never have been waged,” he said.

In addition to the US deaths, tens of thousands of Iraqi civilians have been killed in the war.