Insurgent intimidation of Iraqi soldiers has hampered U.S. efforts to build a reliable security force, the U.S. general in charge of training Iraqi troops said Friday.

Army Lt. Gen. David Petraeus (search), speaking from Baghdad to reporters at the Pentagon, said the Iraqi units had suffered "losses due to severe intimidation," but he offered no specifics.

He did not cite an absentee or desertion rate.

By next week, when 3,500 replacements become available for duty, the 90 battalions of police, army and other types of security forces will be at 80 percent of their intended manpower levels, Petraeus said.

But referring to the overall state of training, Petraeus said "considerable momentum has been achieved" toward reaching the point where Iraqi forces can take the lead role in fighting the insurgency. He said Iraqis already are taking the lead in 12 of the country's 18 provinces.

Getting the Iraqis ready to handle their own security is the key to lowering the U.S. troop presence there.

On Thursday, Deputy Defense Secretary Paul Wolfowitz (search) said that with the election in Iraq over he believes some 15,000 U.S. troops can be withdrawn in the short run, reducing the American military force to 135,000.

"I think we'll be able to come down to the level that was projected before this election," Wolfowitz told the Senate Armed Services Committee.

Still, he struck a caution tone in his appearance before the committee on Thursday, warning that "Iraq still faces a difficult road ahead to defeat the terrorist threat and achieve stability, much less freedom and democracy."

Defense Secretary Donald H. Rumsfeld (search) told reporters at a Pentagon news conference he believes the elections may stiffen the resolve of ordinary Iraqis to fight in cooperation with American forces.

"I expect that level of violence and the insurgency to continue," Rumsfeld said. But at the same time, the voting may have marked a "tipping point" at which Iraqis who had been intimidated by the insurgents decide to step forward and join the army or other security force or provide useful information to U.S. forces, he said.

"I think it means that intelligence is going to improve, I think that it means that there will be more people who will be willing to provide information ... about people who were trying to intimidate them and control their cities, and over time" support for the government will grow, he said.

Rumsfeld also said U.S. forces are making good progress in training Iraqi security forces, but he cautioned that it was a gradual process.

"Nobody should expect that Iraqi security forces are going to come out of some pipeline," he said.

President Bush, meanwhile, brushed aside calls for a withdrawal strategy from Iraq.

"They ask me, 'Is there a timetable for withdrawal from Iraq?' Here's the answer to that: You don't set timetables," Bush said in Great Falls, Mont., during an event to push his idea for Social Security reform.

"You don't want the enemy to say, 'We'll just wait them out,"' he said. "The timetable is as soon as possible, and it's going to be based on the willingness and the capacity of the Iraqi troops to fight the enemy."

Some Democrats on the armed services panel made clear they want U.S. troops to return immediately.

"When are the Iraqis going to fight for their own country? When are they going to start shedding their own blood ... as American servicemen with this amount of training are ready to shed theirs," said Sen. Edward Kennedy, D-Mass.

Sen. Carl Levin, D-Mich., and Sen. John McCain, R-Ariz., both pressed for an estimate on how many insurgents U.S. and Iraqi forces are battling.

"I don't know how you defeat an insurgency unless you have some handle on the number of people that you are facing," McCain said. "I think the American people should know the nature of the enemy that we are facing."