The Bush administration is developing what are described as concepts for reducing American combat forces in Iraq by as much as half next year, according to senior administration officials in the midst of the internal debate.
It is the first indication that growing political pressure is forcing the White House to turn its attention to what happens after the current troop increase runs its course.
The concepts call for a reduction in forces that could lower troop levels by the midst of the 2008 presidential election to roughly 100,000, from about 146,000, the latest available figure, which the military reported on May 1. They would also greatly scale back the mission that President Bush set for the American military when he ordered it in January to win back control of Baghdad and Anbar Province.
The mission would instead focus on the training of Iraqi troops and fighting Al Qaeda in Mesopotamia, while removing Americans from many of the counterinsurgency efforts inside Baghdad.
Still, there is no indication that Mr. Bush is preparing to call an early end to the current troop increase, and one reason officials are talking about their long-range strategy may be to blunt pressure from members of Congress, including some Republicans, who are pushing for a more rapid troop reduction.
The officials declined to be quoted for attribution because they were discussing internal deliberations that they expected to evolve over several months.