U.S. Sen. Bernie Sanders is leading a long-shot effort to halt a $735 million arms sale to Israel as Democrats in the U.S. Congress raise mounting concerns about the violence in the Middle East.

The Vermont senator introduced a resolution on Thursday to block the weapons transfer. A similar measure in the House was introduced Rep. Alexandria Ocasio-Cortez, a Democrat from New York, and liberal lawmakers on Wednesday.

Sanders says that Congress needs to “take a hard look at whether the sale of these weapons is actually helping, or whether it is simply fueling conflict.”

Supporters of this effort are unlikely to have the votes needed to reverse the sale, but they’re racing the clock to register opposition under a review period that expires this week.

The opposition to what had been a routine transfer of arms shows the increasing unrest on Capitol Hill from some Democrats over Israel’s allegedly “disproportionate” handling of the conflict with Hamas in Gaza.

(Vosizneias).