White House spokesman Dana Perino said it "may be possible" that the president decides by Friday to continue withdrawing troops after an initial drawdown ends in July, or take a brief pause to assess the situation.

Bush was due to chair a National Security Council meeting later Monday with a video link to General David Petraeus, who oversees US forces in Iraq, and the US ambassador to Baghdad, Ryan Crocker.

"I don't expect him to say anything prior to the testimony that Petraeus and Crocker will provide (to Congress) that second week of April," she added.

An initial drawdown from 158,000 to 140,000 troops is planned to be completed in July, but Petraeus and Defense Secretary Robert Gates are in favor of a pause before any further withdrawal.

Asked about the president's thinking, Perino said it was "not unlikely" that he would accept a pause after July, saying: "The president thinks that there's some merit in that recommendation."

She added that Monday's talks with Petraeus and Crocker were a chance to receive "their best thinking as to where we are right now and what they think they would like to recommend to the commander in chief."

She was speaking the day after four US soldiers were killed in a roadside bomb in Baghdad, bringing the American death toll in Iraq since the US-led invasion in 2003 to 4,000.

Bush "obviously is grieved by the moment, but he mourns the loss of every single life from the very first that was lost in this conflict to the ones that are lost today," Perino said of the grim milestone.

"And he bears the responsibility for the decisions that he made and he also bears the responsibility to continue to focus on succeeding."

Vice President Dick Cheney, on a visit to Jerusalem, said earlier that reaching the 4,000-mark "may have a psychological effect on the public but it's a tragedy that we live in a kind of world where that happens."

At least 97 percent of the US casualties occurred after Bush announced the end of "major combat" in Iraq on May 1, 2003.

Despite the losses, the president used a speech on the eve of the war's fifth anniversary last week to defend his decision to invade and to reject any notion of retreating despite the "high cost in lives and treasure."

© 2008 Agence France-Presse