WASHINGTON — The top U.S. military commander in Iraq said Wednesday that he is unlikely to call for another troop buildup in Iraq, even if security deteriorates after the extra American soldiers return home this summer.

Gen. David Petraeus told a House panel that such a move would be considered the last resort, in part because of the strain it would place on the Army. First, the military could try to reallocate existing troops to respond to any hotspots. It also would rely more on Iraqi forces, which are improving in capability, he said.

"That would be a pretty remote thought in my mind," he said of reinstating last year's influx of troops.

Petraeus has recommended to President Bush that the U.S. complete, by the end of July, the withdrawal of the 20,000 troops that were sent to Iraq last year to calm the violence there. Beyond that, the general proposed a 45-day evaluation period, to be followed by an indefinite period of assessment before he would recommend any further pullouts.

"We think it makes sense to have some time, to let the dust settle, perhaps to do some adjustment of forces, re-evaluation," he told the House Armed Services Committee.

Bush is to address the nation on his decision about troop levels in Iraq at 11:30 a.m. EDT Thursday from the Cross Hall of the White House. Aides signaled — as the president has for weeks — that he would likely embrace Petraeus' recommendations. White House press secretary Dana Perino also said it is "within the realm of possibility" that Bush would discuss the length of soldiers' tours of duty in Iraq. She wouldn't be specific, citing the ongoing testimony and Bush's meeting Wednesday afternoon with congressional leaders.

"I think the president has gotten a lot of advice," she said. "I think he's pretty far down the path of what he's going to say tomorrow."

Wednesday's hearing marked the second day of testimony by Petraeus and Ryan Crocker, the U.S. ambassador in Iraq. Both described Iraq as a fragile state and warned that hard-fought security gains could slip if troops leave too soon.

Democrats said pausing troop reductions would signal to the Iraqis that the United States was committed to the war indefinitely.

"Political reconciliation hasn't happened, and violence has leveled off and may be creeping back up," said Rep. Ike Skelton, D-Mo., chairman of the House committee. "So how can we encourage, if not force, the intransigent political leaders of Iraq to forge a real nation out of their base sectarian instincts?"

Republicans were considerably more optimistic about the situation in Iraq than last year.

"No one can deny that the security situation in Iraq has improved," said Rep. Duncan Hunter of California, the No. 1 Republican on the committee.

When pressed by Skelton, the four-star general said he can envision more troops leaving after July.

"I can foresee the reduction beyond the 15" Army brigades that will be left behind in Iraq this summer, he said. But like Tuesday, he refused to give senators any kind of timetable: "The question is at what pace that will take place," he said.

Petraeus said the health of U.S. ground forces was a "major strategic consideration" in his recommendation and will continue to be a factor in his assessments. The administration is expected to announce this week that combat tours will be reduced from the current 15 months to 12 months, regardless of the 45-day pause in troop withdrawals.

"I am keenly aware of the strain," Petraeus said. Having been deployed himself since 2001, "this is something that my family and I do know a great deal about personally."

On progress made by Iraqi forces, Petraeus said Baghdad's security units represent "a very, very mixed bag across the board." In the recent Basra operation, the Iraqis displayed an impressive ability to deploy themselves. But the fight itself was hastily done with many units unprepared for battle, he said.

Petraeus and Crocker reiterated their message before the House Foreign Affairs Committee, and again faced Democrats who suggested the U.S. was embroiled in an indefinite commitment.

"When does this end?" asked Rep. Gary Ackerman, D-N.Y.

Lacking the votes to order troops home by a certain date, Democrats plan to push legislation this spring that would force the Iraqi government to spend its own surplus in oil revenues to rebuild the country, sparing U.S. dollars. Many Republicans have signaled their concerns about burgeoning Iraqi oil revenues at a time when the war is growing increasingly costly.

"This nation is facing record deficits and the Iraqis have translated their oil revenues into budget surpluses rather than effective services," Skelton said. "Under these circumstances and with the strategic risk to our nation and our military readiness, we and the American people must ask — why should we stay in Iraq in large numbers?"