Washington ? U.S. military planners have begun plotting a fallback strategy for Iraq that includes a gradual withdrawal of forces and a renewed emphasis on training Iraqi fighters in case the current troop buildup fails or is derailed by Congress.

Such a strategy, based in part on the U.S. experience in El Salvador in the 1980s, is in the early planning stages and would be adjusted to fit the outcome of the current surge in troop levels, according to military officials and Pentagon consultants who spoke on condition of anonymity.

But a drawdown of forces would be in line with comments to Congress by Defense Secretary Robert M. Gates last month that if the surge fails, the backup plan would include moving troops “out of harm’s way.” Such a plan also would be close to recommendations of the Iraq Study Group, of which Gates was a member before his appointment as Defense chief.

A strategy following the El Salvador model would be a dramatic break from President Bush’s policy committing large numbers of U.S. troops to aggressive counterinsurgency tactics, but it has influential backers within the Pentagon.

“This part of the world has an allergy against foreign presence,” a senior Pentagon official said. “You have a window of opportunity that is relatively short. Your ability to influence this with a large U.S. force eventually gets to the point that it is self-defeating.”

The new round of planning is taking place in an atmosphere of extraordinary tension within the Pentagon, which is grappling with a war about to enter its fifth year and going poorly on the ground while straining U.S. forces worldwide.

At the same time, the war has created divisions within the Pentagon. Some support the new commander in Iraq, Gen. David H. Petraeus, who advocates using more U.S. forces to protect Baghdad neighborhoods, while others back the position of Gen. John P. Abizaid, the retiring commander for the Mideast, who favored handing responsibility more quickly to Iraqis.

A shift from the buildup and toward a more adviser-based strategy would bring the administration more in line with the Iraq Study Group, a bipartisan panel created by Congress to make war recommendations. The group called for a gradual reduction in U.S. combat forces. Kalev I. Sepp, a key adviser to the panel and an El Salvador veteran, was instrumental in getting the commission to back an expanded advisory effort.

“That’s exactly what I proposed to the Iraq Study Group, and that’s exactly what ended up in the report,” said Sepp, an instructor at the Naval Postgraduate School in Monterey, Calif.

The El Salvador case study contrasts with the soldier-heavy example of Vietnam and the current buildup in Iraq. In El Salvador, the United States sent 55 Green Berets to aid the Salvadoran military in its fight against rebels between 1981 and 1992, when peace accords were signed.

Years later, the U.S. role in El Salvador remains controversial. Some academics have argued that the U.S. military turned a blind eye to government-backed death squads or even aided them. But former advisers and military historians argue that the United States gradually professionalized the Salvadoran army and curbed the government’s abuses.

In recent congressional hearings and in private Pentagon meetings, Marine Gen. Peter Pace, chairman of the Joint Chiefs of Staff, has made several references to the El Salvador campaign.

The senior Pentagon official said Pace’s repeated references were a signal that in the chairman’s view, success in Iraq might not depend on more combat troops.

There is a “sweet spot we are trying to hit,” the senior official said. “We need enough American presence to ensure (Iraq) doesn’t go down, without paying the price of a large U.S. profile that then triggers all the downsides.”

Some current and former military officers note that the United States has a better track record at fighting insurgencies with small numbers of advisers than it does with large campaigns.