WASHINGTON — As the Bush administration mulls options for withdrawing forces in Iraq, fault lines are beginning to emerge in a debate between commanders in the field who favor slow reductions and senior generals at the Pentagon who favor cutting the number of combat troops more deeply.
Among others, Gen. Peter Pace, the chairman of the Joint Chiefs of Staff, and Gen. George W. Casey Jr., the Army chief of staff, are said to be leaning toward a recommendation that steep reductions by the end of 2008, perhaps to half of the 20 combat brigades now in Iraq, should be the administration's goal.
Such a reduction would be deeper and faster than Gen. David H. Petraeus, the top commander in Iraq, is expected to recommend next month, administration officials said.
"If you're out in Baghdad you might have a different priority for where you want the troops," an administration official said, speaking only on condition of anonymity because the White House has not authorized public remarks on the options being considered.
It has been known since the spring that the White House was considering options for reducing combat forces in Iraq by almost half in 2008, which could bring overall troop levels below 100,000. But the shape of the debate is only beginning to emerge.
On the war front Friday, U.S. helicopters blasted rooftops in a Shiite neighborhood before dawn Friday as American troops battled gunmen on the ground, killing at least eight by the military's count. Shiites said some civilians died, and radicals castigated Iraq's government as being too weak to rein in the Americans.
The criticism put new pressure on the Shiite prime minister, Nouri al-Maliki, who already was under fire from U.S. critics over his government's failure to achieve national unity.
Elsewhere, an explosion killed one American soldier and wounded four in Salahuddin province, a mostly Sunni Arab area north of the capital. The blast came hours after suspected al-Qaida in Iraq fighters attacked police stations in Samarra, a city in the province about 60 miles north of Baghdad. A policeman, a woman and an 11-year-old girl were reported killed.
With more than 160,000 troops now in Iraq, Casey warned recently, "We're consumed with meeting the current demands and we're unable to provide ready forces as rapidly as we would like for other contingencies. He added: "This is a temporary state, and one we must pass through quickly if we're going to preserve and sustain our all-volunteer force and restore strategic depth."
But the assessment Petraeus is preparing to deliver next month is likely to call for at most modest reductions in troop levels by next spring. At that point the five additional brigades added this year under the president's troop increase are likely to be withdrawn gradually.
Administration officials said Bush is acutely aware that some reduction next year will be required, and they said he plans to use next month's debate to outline a plan for gradual troop reductions. He has not decided on a timetable or whether to go beyond pulling out the five additional brigades, officials said.
"At this point the only question is when the drawdown begins and how fast it proceeds," said one senior administration official who has been deeply involved in the internal debate. "But to get there, something has to give."
White House officials said that Bush had yet to receive a formal proposal from Pace or other officials about how large a troop withdrawal to make.
"The president has received no recommendation regarding our future force posture in Iraq," Gordon D. Johndroe, a White House spokesman, told reporters in a briefing at Crawford, Texas. He was responding to the report in The Los Angeles Times.
In a statement, Pace said he could not comment on what size withdrawal he would recommend. "I have not made or decided on any recommendations yet," he said, adding: "I take very seriously my duty to provide the best military advice to the president. I provide that advice privately to the president."
With violence in Iraq expected to remain high into next year, for the United States to reach a force level of 10 brigades by late 2008 may be impossible, several Pentagon officials conceded. Bush and his commanders may decide on a less ambitious goal of reaching a force level of 12 to 15 brigades, and even that could be dependent on improvement in security conditions and in the Iraqi forces' capabilities, they said.
What Bush announces next month may also be constrained to some extent by his warnings in recent months that publicizing a withdrawal could embolden the enemy in Iraq. He also has to take into account an assessment released this week by the nation's intelligence agencies that cautioned that reducing forces too quickly could jeopardize recent security gains.
Complicating his decision-making further, Bush must balance the views of field commanders against those of members of Congress, who appear increasingly interested in seeing troop reductions later this year.
In a briefing by video for Pentagon reporters Friday, Maj. Gen. Rick Lynch, commander of the 3rd Infantry Division in Iraq, warned against starting to remove U.S. troops later this year, an idea favored by many Democrats and one also endorsed this week by Sen. John W. Warner, a senior Republican from Virginia. Warner, a longtime member of the Armed Services Committee, said that Bush should announce a pullout of troops, even if only a small number, to pressure the Iraqi government to make political compromises.
"What would happen is the enemy would come back," Lynch said. "He'd start building the bombs again, he'd start attacking the locals again, he'd start exporting that violence to Baghdad. We would take a giant step backwards."
Pace, who was not nominated for a second term as Joint Chiefs chairman, is due to retire at the end of September; presiding as the president's senior military adviser over next month's review is likely to be his final major duty.
Whatever the Joint Chiefs recommend, it will have been coordinated with Petraeus and with Gates in coming weeks in hopes of achieving a consensus position, several Pentagon officials said.
When the decision was made late last year to send nearly 30,000 additional troops to Iraq, Pace served as an intermediary between the White House, which favored a large troop increase, and Casey, the Iraq commander at the time, who wanted fewer, if any, additional troops. But now, as he prepares for retirement, Pace may also feel emboldened to push for a faster withdrawal than his field commander favors.
Casey has long believed that too large an American presence would deter the Iraqi government from assuming the lead role in securing the country. His views were largely rejected when Petraeus was brought in, with a new strategy that called for using large numbers of U.S. forces to protect Iraqis.
Casey has used his new position, as Army chief of staff, to make clear his concerns that the elevated troop levels in Iraq are imposing too large a strain on the Army and his desire to do away with the current 15-month deployments of soldiers in Iraq.
But some Pentagon officials said that Casey, who traveled to Iraq and met with Petraeus this month, still believes that the additional U.S. forces, while helpful in reducing violence, slow the Iraqi government's maturation.