America’s deepening divisions over the war in Iraq were put on show on Wednesday as an embattled President George W. Bush defended his decision to send more troops and insisted he would veto any bill from Congress that set a timetable for US withdrawal.

Mr Bush drew cheers at the National Cattlemen’s Beef Association when he derided Democrats for inserting million of dollars of requests for “tree assistance”, expense accounts and visits to the Capitol into an emergency war spending bill, as well as deadlines for pulling out of Iraq.

“Here’s the bottom line: the House and Senate bills have too much pork, too many conditions on our commanders, and an artificial timetable for withdrawal,’’ Mr Bush said. “And I have made it clear for weeks, if either version comes to my desk, I’m going to veto it.’’

Mr Bush was speaking as the Senate prepared to renew debate on the $122bn spending bill. On Tuesday, the defection of Republican senators Chuck Hagel of Nebraska and Gordon Smith of Oregon – enabled the Democrats to reject a proposed Republican amendment to remove a March 31 2008 withdrawal date from the bill.

The House of Representatives last week passed a similar bill by a 218-212 vote that would remove combat troops by August 31 2008. If the Senate bill passes a final vote then both bills have to reconciled by negotiators from the two chambers before legislation is sent to the president.

Asked how the Democrats would respond to a veto, Nancy Pelosi, speaker of the House, said she would tell Mr Bush: “Calm down with the threats. There is a new Congress in town. We respect your constitutional role; we want you to respect ours.”

“This war must end. The American people have lost faith in the president’s conduct of the war. Let’s see how we can work together,” she told reporters.

She and Harry Reid, the Senate Democratic leader, later released a letter they sent to Mr Bush urging him to “sit down and work together on the bill”.

White House spokeswoman Dana Perino said the president knew the war was unpopular but that he would still reject arbitrary dates for withdrawal. She suggested that Congress should cut short its recess and negotiate the issue.

Opinion polls reveal the president’s isolation. A USA Today/Gallup poll taken after the House vote showed 60 per cent of Americans supported a withdrawal of all US troops from Iraq no later than autumn 2008. Other polls, however, show more Americans starting to think the “surge” in troops might be working, although majorities still do not see the war going well.

Mr Bush cited unnamed Iraqi bloggers as saying conditions were improving.

Only half the extra reinforcements had arrived in Baghdad so far but all should be in place by June, he said. The strategy, led by General David Petraeus, was beginning to show “signs of success”.

Get alerts on Front page when a new story is published

Copyright The Financial Times Limited 2018. All rights reserved.

Comments have not been enabled for this article.

Follow the topics in this article