"Go Big," the first option, originally contemplated a large increase in U.S. troops in Iraq to try to break the cycle of sectarian and insurgent violence. A classic counterinsurgency campaign, though, would require several hundred thousand additional U.S. and Iraqi soldiers as well as heavily armed Iraqi police. That option has been all but rejected by the study group, which concluded that there are not enough troops in the U.S. military and not enough effective Iraqi forces, said sources who have been informally briefed on the review.

"The 'Go Long' approach is one that can work if there is sufficient strategic patience, resources appropriated and [if] leadership executes effectively," a military intelligence official said.

Another potential obstacle to the "Go Long" option is that it runs counter to the impulse of many congressional Democrats to find a way to get out of Iraq quickly. Planners envision taking five to 10 more years to create a stable and competent Iraqi army. Because it wouldn't lead to a swift exit, some Democrats could criticize this option as a disguised version of "staying the course."

"Go Home," the third option, calls for a swift withdrawal of U.S. troops. It was rejected by the Pentagon group as likely to push Iraq directly into a full-blown and bloody civil war.

The group has devised a hybrid plan that combines part of the first option with the second one — "Go Long" — and calls for cutting the U.S. combat presence in favor of a long-term expansion of the training and advisory efforts. Under this mixture of options, which is gaining favor inside the military, the U.S. presence in Iraq, currently about 140,000 troops, would be boosted by 20,000 to 30,000 for a short period, the officials said.

The purpose of the temporary but notable increase, they said, would be twofold: To do as much as possible to curtail sectarian violence, and also to signal to the Iraqi government and public that the shift to a "Go Long" option that aims to eventually cut the U.S. presence is not a disguised form of withdrawal.

Even so, there is concern that such a radical shift in the U.S. posture in Iraq could further damage the standing of its government, which U.S. officials worry is already shaky. Under the hybrid plan, the short increase in U.S. troop levels would be followed by a long-term plan to radically cut the presence, perhaps to 60,000 troops.

That combination plan, which one defense official called "Go Big but Short While Transitioning to Go Long," could backfire if Iraqis suspect it is really a way for the United States to moonwalk out of Iraq — that is, to imitate singer Michael Jackson's trademark move of appearing to move forward while actually sliding backward. "If we commit to that concept, we have to accept upfront that it might result in the opposite of what we want," the official said.

On the other hand, the hybrid version of "Go Long" may be remarkably close to the recommendation that the Iraq Study Group, led by former secretary of state James A. Baker III and former representative Lee H. Hamilton (D-Ind.). That group's findings, expected to be issued next month, are said to focus on changing the emphasis of U.S. military operations from combating the insurgency to training Iraqis, and also to find ways to increase security in Baghdad and bring neighboring countries into talks about stabilizing Iraq.