WASHINGTON — The Pentagon has begun to look seriously at creating military forces that would be dedicated to peacekeeping and reconstruction after future conflicts, defense officials said.

The idea is to forge deployable brigades or even whole divisions out of units of engineers, military police, civil affairs officers and other specialists critical to postwar operations.

The move marks a reversal for the Bush administration, which came into office strongly resistant to peacekeeping missions and intent on trying to get Europeans and other allies to shoulder more of that burden.

It also comes in the face of traditional U.S. Army opposition to the idea of establishing forces focused on peacekeeping. Army officials have argued that combat troops can be used for peacekeeping when necessary and that additional units with recovery-related skills can be cobbled onto combat divisions to meet postwar demands.

But in Iraq, U.S. forces have struggled to deal with insurgents and other postwar challenges, and help from other foreign countries has fallen far short of initial U.S. expectations. Facing widespread criticism for poor postwar planning, and concerned that peacekeeping may become more of a norm for the U.S. military, senior Pentagon officials are being driven to consider alternative ways of organizing troops for postwar operations.

"This mission is too important and too hard to rely on cobbling," said Arthur Cebrowski, director of the Office of Force Transformation, who has become a leading advocate of designing forces specifically for what the Pentagon now calls postwar "stability operations."

Defense Secretary Donald Rumsfeld has taken an interest in the notion. In a brief memo to subordinates in August, Rumsfeld raised the question of whether the Pentagon should "try to fashion a … post-combat capability of some sort," according to a recipient of the memo.

As a further sign the issue is receiving high-level attention, language is being drafted for the Strategic Planning Guidance — the classified document that provides a basis for Pentagon budgeting and programming — that would direct military authorities to explore setting up a stability operations force.

A September study by the Pentagon’s Office of Stability Operations outlined how a brigade-size force of about 5,000 troops could be organized. Another study, sponsored by Cebrowski and completed earlier this month by a National Defense University team, called for an even larger force of two division-size elements — one active-duty, one reserve — totaling about 30,000 troops.

"It’s an idea that has legs," said another senior defense official involved in the discussions. "If you have dedicated forces, you can ensure they will be better organized for postwar tasks and will know better what they’re about."

One alternative, short of a permanent new force, would involve earmarking certain troops for stability operations for a limited period of time — say, several years — after which they would return to combat status. Another possibility, officials said, would be to expose all troops to more training in post-conflict scenarios.