Updated

The Pentagon (search) is laying the groundwork for beginning a withdrawal from Iraq (search), even as it is weighing the risk of moving so quickly that Iraqi security forces collapse without U.S. support.

The benefits of a U.S. pullout are pretty clear. Fewer troops would likely mean fewer casualties and less strain on the Army and Marine Corps, which already are stretched thin. And it would lessen the degree to which the presence of foreign forces fuels an anti-U.S. terrorist insurgency.

There are now about 138,000 U.S. troops in Iraq in a war with dwindling popularity among American voters.

At best, a U.S. drawdown would begin shortly after elections for a new government in Baghdad (search), scheduled for December. That assumes two other difficult political milestones are achieved first: drafting a constitution by Aug. 15 and holding a national referendum in mid-October to approve the constitution.

It also assumes the terrorist insurgency does not get worse — and that Iraqi security forces prove themselves ready for combat.

If the U.S. were to withdraw before the Iraqis were ready, the American sacrifices of the past 21/2 years could be lost — and President Bush (search) would face pressure to explain why the invasion was worth it.

Even though Defense Secretary Donald H. Rumsfeld (search) has not yet received even a recommendation from commanders on when to start the pullout, he has been talking more directly in recent days about the security transition.

"Once Iraq is safely in the hands of the Iraqi people, and a government they elected under a new constitution, our troops will be able to come home with the honor they have earned," Rumsfeld said in a speech prepared for the Dallas Chamber of Commerce on Tuesday. Rumsfeld delivered only abbreviated remarks by telephone after his plane had mechanical problems.

Noticeably absent from his comments was any assertion that defeating the terrorist insurgency is one of the conditions for an American withdrawal.

In Rumsfeld's view, shared by top U.S. commanders in Iraq, it must be left to the Iraqis to overcome the terrorist insurgency. Likewise, the Iraqis must be prodded to take the lead in other areas of their struggle to rebuild.

Among the signs that the United States is pressing a faster transition to Iraqi-led security, to open the way for a U.S. withdrawal:

— After taking up his post last month as U.S. ambassador to Baghdad, Zalmay Khalilzad announced the creation of a U.S.-Iraq task force to develop a strategy and conditions for transferring the security responsibility from the U.S.-led coalition forces to the Iraqis. "Our common goal is to help Iraq stand on its own feet as quickly as possible," Khalilzad said, adding that this would allow for a phased U.S. pullout.

— Last weekend Iraqi police and a brigade of the 5th Iraqi Army Division formally took full control of an area in Diyala Province, to the northeast of Baghdad, known as Khalis Qadah, replacing a U.S. Army unit. Col. Archie Davis, spokesman for Gen. George Casey, the top U.S. commander in Iraq, said the transition was made because the Iraqis had demonstrated their proficiency at fighting the terrorists without U.S. support.

— Mowaffak Rubaie, Iraq's national security adviser, said Monday that several cities in the more stable south and north had been identified as areas where withdrawal of foreign forces could likely start soon. The cities included Najaf, Karbala, Samawah, Diwaniyah and Nasiriyah in the heavily Shiite Muslim south, and possibly Irbil and Sulaymaniyah in the predominantly Kurdish north.

The battle against the terrorist insurgency brought another stark reminder Tuesday of the cost in U.S. lives of remaining in Iraq. Military officials announced that seven Marines were killed in action on Monday, pushing the total number of U.S. deaths in Iraq since the March 2003 invasion beyond the 1,800 mark. More than 13,700 have been wounded.

Iraqis — both civilians and security forces — have taken the lion's share of the casualties in recent months as U.S. troops have deliberately scaled back their unilateral combat missions to operate more with Iraqi forces. There are now more than 180,000 Iraqi police and army troops that have been trained and equipped by U.S. forces.

On a visit to Iraq last week, Rumsfeld drew a direct link between American combat deaths and the urgency of getting the Iraqis to complete a constitution by Aug. 15.

"We have troops on the ground there. People are getting killed," Rumsfeld said, adding that "political progress is necessary to defeat the insurgency."