WASHINGTON (Reuters) - President George W. Bush said on Thursday he would suspend U.S. troop withdrawals from Iraq this summer but cut the length of tours of duty, as he defended his war policy that will leave any resolution of the conflict to his successor.

Slideshow ( 4 images )

Bush endorsed a recommendation by his commander in Iraq, Gen. David Petraeus, to complete a limited withdrawal of combat forces by July but then impose a 45-day freeze on the total number of troops at about 140,000 to assess the security situation before considering more cuts.

“I’ve told him he’ll have all the time he needs,” Bush said.

Petraeus had told a contentious congressional debate on the costly and unpopular war this week that progress was “fragile and reversible” and a renewed outbreak of violence had killed 20 U.S. troops so far in April.

Under Bush’s plan, the military will complete a withdrawal in July of some 20,000 extra combat troops deployed in the last year but then pause before deciding whether more can be pulled out.

Bush has repeatedly said his decisions on U.S. 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 U.S. troops will almost certainly be in Iraq when Bush’s successor takes over in January. Iraq has again become a major issue in the campaign for the November elections.

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

“To ease the burden on our troops and their families, I have directed the secretary of defense to reduce deployment lengths from 15 months to 12 months,” Bush said.

The changes would be effective for troops deploying starting August 1, Bush said at the White House before leaving for a long weekend at his ranch in Crawford, Texas.