U.S. President George W. Bush suspended on Thursday further U.S. troop withdrawal from Iraq beyond July and cut Army combat troops in Iraq from 15 months to 12 months.

By announcing the two decisions, the president endorsed plans that were proposed by David Petraeus, top U.S. commander in Iraq, during his testimony on the Capitol Hill in the previous two days.

Bush said Petraeus has requested additional time to assess whether the U.S. military can maintain the recent security improvements with fewer U.S. troops on the ground.

"I told him he'll have all the time he needs," the president said.

Accepting another recommendation from Petraeus, Bush said he will reduce combat tours from 15 to 12 months.

However, the shortened tours would apply only to troops deployed on or after Aug. 1 and would not cutback tours for those currently in Iraq.

"Our nation owes a special thanks to the soldiers and families who have supported this extended deployment," Bush said.

The president also warned Iran against arming Shiite militants in Iraq, saying Iran "has a choice to make."

"If Iran makes the wrong choice, America will act to protect our interests, our troops and our Iraqi partners," he said.