WASHINGTON, Nov 18 (Reuters) - 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 "resolutions of disapproval" were filed by Senator Bernie Sanders, an independent who caucuses with Democrats. Strong bipartisan support for Israel means the resolutions are not expected to pass, but backers hope they will encourage Israel's government and President Joe Biden's administration to do more to protect civilians in Gaza.

Most of Gaza's population of 2.3 million people has been displaced and the enclave is at risk of famine. Gaza health officials say more than 43,922 Palestinians have been killed in Israel's 13-month-old offensive.

Two of the resolutions, co-sponsored with Democratic Senators Jeff Merkley and Peter Welch, would block the sale of 120 mm mortar rounds and joint direct attack munitions (JDAMS). A third, sponsored by Democratic Senator Brian Schatz, would block the sale of tank rounds.

JDAM tail kits, which convert a standard unguided bomb using fins and a GPS guidance system into a guided weapon, are made by Boeing (BA.N), opens new tab.

"This war has been conducted almost entirely with American weapons and $18 billion in U.S. taxpayer dollars. Israel has dropped U.S.-provided 2,000-pound bombs into crowded neighborhoods, killed hundreds of civilians to take out a handful of Hamas fighters, and made little effort to distinguish between civilians and combatants," Sanders said in a statement.

"These actions are immoral and illegal," he said.

Biden, whose term ends in January, has strongly backed Israel since Hamas-led gunmen attacked in October 2023, killing 1,200 people and taking more than 250 hostages, according to Israeli tallies.

The Biden administration in October told Israel that it had 30 days to improve the flow of aid to Gaza or risk consequences to U.S. military aid.

After that period, Washington said on Nov. 12 it concluded that Israel had made progress and was not currently impeding assistance to Gaza. Many aid groups disagreed.

Israel says it has been working to address humanitarian needs and the main problem with aid deliveries was U.N. distribution challenges.

Democratic Senator Chris Van Hollen on Monday said he supported the joint resolutions of disapproval, as did Democratic Senator Elizabeth Warren last week.

U.S. law gives Congress the right to stop major foreign weapons sales by passing resolutions of disapproval. Although no such resolution has both passed Congress and survived a presidential veto, the law requires the Senate to vote if a resolution is filed. Such resolutions have at times led to angry debates embarrassing to past presidents.