Baghdad, Iraq ? Senior U.S. military commanders in Iraq say it is increasingly likely they will need a further increase in combat forces to put down remaining areas of resistance in the country.

Convinced that the recent battle for Fallujah has significantly weakened insurgent ranks, commanders here have devised plans to press the offensive into neighborhoods where rebels have either taken refuge after fleeing Fallujah or were already deeply entrenched.

But the forces available for these intensified operations have become limited by the demands of securing Fallujah and overseeing the massive reconstruction effort there — demands that senior U.S. military officers say are likely to tie up a substantial number of Marines and Army troops for weeks.

“What’s important is to keep the pressure on these guys now that we’ve taken Fallujah from them,” a high-ranking U.S. military commander said, speaking on condition he not be named.

The possibility that additional troops would be required to battle the insurgency in this critical period preceding the Iraqi elections has been signaled for weeks. The Pentagon took an initial step in this direction last month, ordering about 6,500 soldiers in Iraq to extend their tours by up to two months.

The officers said the exact number of extra troops needed was still being reviewed.