Some of the options being considered for the revised Authorization for the Use of Military Force include a 60-day period for Obama to launch “narrow, limited” strikes against Assad’s regime with the potential for a 30-day extension of that deadline.

Language barring the insertion of U.S. ground troops — but crafted to allow special forces operations or the rescue of a downed American flier, for instance — is also being considered, the sources said.

And Obama would be prohibited from making the toppling of Assad’s government the goal of any U.S. military effort in Syria, as some some hawkish lawmakers have supported.

The revisions are designed to win broad bipartisan backing from senators who are on the fence over whether to back a Syria campaign, GOP and Democratic sources said.