Ten hawkish Democratic senators vowed Jan. 27 to vote against Iran sanctions legislation if it comes up before the end of March, robbing Republicans of the votes they need to override a veto.

The announcement is a clear win for President Barack Obama, who has repeatedly warned lawmakers that targeting Iran now could blow up delicate diplomatic talks. The latest development all but assures that the Senate leadership will delay a vote rather than turn Iran into a partisan issue, with even top Republicans making that case.

“The last thing we need to do is pass a bill out of the U.S. Senate that is not veto proof,” Senate Foreign Relations Chairman Bob Corker, R-Tenn., tweeted Jan. 27.

The lawmakers made the announcement in a letter to Obama spearheaded by Iran sanctions co-author Robert Menendez, D-N.J., and signed by most of the Democrats who supported such legislation in the past. The signers say they’re “deeply skeptical” Iran will reach a political framework agreement by March 24 as called for under the current talks, but agreed to abide by Obama’s “concern” that passing sanctions legislation now could doom talks and unravel international support for the current sanctions regime.