WASHINGTON — The Pentagon’s decision to lift the ban on women serving in combat presents a challenge to top military leaders who now will have to decide which, if any, jobs they believe should be open only to men.

Defense Secretary Leon Panetta is expected to announce today that more than 230,000 battlefront posts — many in Army and Marine infantry units and in potentially elite commando jobs — are now open to women. It will be up to the military service chiefs to recommend and defend whether women should be excluded from any of those more demanding and deadly positions, such as Navy SEALs or the Army’s Delta Force.

The historic change, which was recommended by the Joint Chiefs of Staff, overturns a 1994 rule prohibiting women from being assigned to smaller ground combat units.

The change won’t take place overnight: Service chiefs will have to develop plans for allowing women to seek the combat positions, a senior military official said. Some jobs may open as soon as this year, while other assessments, such as special operations forces, might take longer.

There long has been opposition to putting women in combat, based on questions of whether they have the necessary strength and stamina for certain jobs, or whether their presence might hurt unit cohesion.

But as news of Panetta’s expected order got out, many members of Congress, including the Senate Armed Services Committee Chairman, Sen. Carl Levin, D-Mich., announced their support.

“It reflects the reality of 21st century military operations,” Levin said.