The U.S. Senate is due to vote on Wednesday on legislation that would block arms sales to Israel, backed by lawmakers who say Israel is obstructing aid shipments desperately needed by Palestinian civilians in Gaza.

The progressive Israel advocacy group J Street is urging senators to vote in favor of several resolutions put forward by Sen. Bernie Sanders (I-VT) to protest U.S. arms sales to Israel, a lobbying boost for Sanders’ effort and a marked shift to the left for J Street.

On Wednesday, the US Senate is expected to vote on a bill that would block the sale of certain types of weapons to Israel, reports Reuters. The agency reports that the bill is backed by lawmakers who argue that Israel is obstructing humanitarian aid urgently needed by Palestinian civilians in Gaza.