Washington ? Before they can present President Bush with any timeline for withdrawing troops from Iraq, Democrats in Congress face the daunting task of reconciling the Senate withdrawal plan passed Thursday with the one approved last week by the House.

The Senate’s timeline – part of the $123 billion war spending bill that passed 51-47, largely along party lines – requires the president to begin bringing troops home within 120 days of enactment and sets a nonbinding “goal” to have most combat forces out of Iraq by the end of next March.

The proposals have prompted repeated veto threats from President Bush, who said he will not sign legislation that limits what military commanders can do in Iraq. Democratic lawmakers are gearing up for a high-stakes showdown with the president.

The House plan mandates a far more restrictive timeline for drawing down U.S. forces, requiring the president to begin withdrawing troops as soon as July 1 and to complete the process no later than next March.

Senate Majority Leader Harry Reid, D-Nev., and House Speaker Nancy Pelosi, D-Calif., have played down the differences between their plans as they present a united front against the White House.

Thursday, Reid insisted the two Democratic-controlled chambers would have few problems reaching a compromise that could pass the House and Senate.

“We don’t have a gap to overcome,” he said. “The ball is in the president’s court. That’s who has to make the next move.”

Complications ahead

There already were signals of the potential complications that lie ahead, however.

Freshman Rep. Keith Ellison, D-Minn. – a vehement war opponent who was among the last liberals to get behind the House measure last week – said Thursday he would actively work against any bill that did not retain the House’s firm timelines.

“The timelines and the deadlines are the only thing that got me to support it,” said Ellison, who has called for a quick conclusion to the war. “And even then, that was a stretch.”

Under the House plan, the administration will have to certify on July 1 that the Iraqi government is making substantial progress in meeting a set of benchmarks to achieve political reconciliation and reduce sectarian violence. If the president cannot do that, he would have to withdraw most U.S. combat troops by the end of the year.

Even if the Iraqi government meets all the benchmarks, troop withdrawals must begin no later than March 1, 2008, and be completed by the end of that August, according to the House bill.

The absolute deadlines were key to winning the support of staunch anti-war lawmakers in the House, such as Ellison, many of whom have complained that Congress has not moved aggressively enough to end the war. Those lawmakers – who belong to the more than 80-strong Out of Iraq caucus – provided the final votes that guaranteed the 218-212 passage last week. And at least one, Rep. Lloyd Doggett, D-Texas, was promised by Pelosi that House leaders would insist that the timelines remain in any compromise measure worked out with the Senate.

Several members of the Out of Iraq caucus, including Ellison, said this week they are optimistic that Pelosi and her lieutenants would negotiate a compromise they could support.

Support may evaporate

But Ellison was not the only one to sound a warning.

Rep. Jerrold Nadler, D-N.Y., who had urged his colleagues in the Out of Iraq caucus to back the House bill, cautioned that softening the deadlines for a U.S. withdrawal would risk defections.

“If we substantially weaken the timelines, I’d have a real problem with that,” he said.

Those restrictive deadlines, however, could cause support to evaporate for the bill in the Senate.

Senate Democratic leaders were able to unite their caucus behind the spending bill passed Thursday by explicitly omitting a firm deadline for the final withdrawal of combat troops from Iraq.