In a statement at the White House later on Thursday, Mr Bush was due to endorse recommendations by his commander in Iraq, General David Petraeus, who told a contentious congressional debate on the costly and unpopular war this week that progress was 'fragile and reversible'.

The US military will now complete a withdrawal in July of some 20,000 extra combat troops deployed in the last year but then impose a 45-day freeze to assess the security situation before considering further cuts.

Gen Petraeus 'wants to wait and see. And I strongly support that', Mr Bush told the Weekly Standard magazine in an online interview published on Thursday before the president made his statement. 'And therefore (I) won't commit beyond July.'

Mr Bush has repeatedly said his decisions on US troops in Iraq would be based on advice from commanders on the ground and he has opposed setting timetables for withdrawal.

His decision means that more than 100,000 US troops will almost certainly be in Iraq when Mr Bush's successor takes over in January after elections this November.

The president, under pressure over strains on the US military created by the demands of Iraq, will announce that the tour of duty for troops in Iraq and Afghanistan will be reduced to one year from 15 months now served.

'The goal for the active duty force is going to be 12 months in, and a minimum of 12 months out,' White House spokeswoman Dana Perino said.

The policy will affect troops deploying starting Aug 1, she said.

'And we think that that will start to help deal with the stress issues in regards to these deployments, especially people who have been deployed several times,' Ms Perino said.

Limited political progress

The 'surge' of extra forces in the last year helped bring down unprecedented levels of violence throughout Iraq.

But Mr Bush's critics complain the Iraqis themselves have failed to take advantage of that relative lull to make progress toward greater political and security stability that would allow further US troop cuts.

With news of a suspension of withdrawals and renewed violence in which 20 US personnel have died in the first week of April, the war has again emerged as a major issue in the campaign for the November presidential elections.

Mr Bush met Gen Petraeus and Ryan Crocker, the US ambassador to Iraq, over breakfast at the White House and is due to make the Iraq statement at 11:30am local time before leaving for a long weekend at his ranch in Crawford, Texas.

Gen Petraeus and Mr Crocker painted a somber picture of the situation in Iraq in testimony to Congress on Tuesday and Wednesday, which Democrats said gave no sign of an exit strategy after five years of war.

The United States has 160,000 troops in Iraq after boosting the force last year in a bid to reduce violence enough to allow Iraqi lawmakers to enact measures seen as critical to long-term stability.

Tens of thousands of Iraqis and more than 4,000 US troops have died since the 2003 US-led invasion. -- REUTERS