With mounting evidence Israel is breaking legal standards — and its promises to the U.S. — during its ongoing military offensive in Gaza, the Biden administration should stop sending the Israelis weapons and launch a public review of Israeli conduct, a coalition of more than 20 foreign policy and human rights groups argued in a letter to President Joe Biden and his top advisers on Tuesday.

Without a change, the Biden administration’s policy will “continue to cause devastating harm and risk making the United States complicit in war crimes,” argues the message, which was shared exclusively with HuffPost after it was sent to the U.S. National Security Council.

Among its signatories are prominent advocacy groups, such as the nonprofit Center for Civilians in Conflict; humanitarian organizations, like Refugees International; and other bodies from churches to think tanks. Notably, the letter is directed not only to Biden and his senior staff, but also to Vice President Kamala Harris and her national security adviser, Phil Gordon. Many observers hope Harris, who is running to succeed Biden, will be less deferential to Israel than Biden has been since the Oct. 7 attack by the Palestinian group Hamas that began the current fighting, and particularly that as a former prosecutor, she will prioritize U.S. and international law.

The joint statement argues Biden’s current approach of sending Israel billions in military equipment conflicts with one of his own policies: National Security Memorandum 20, or NSM-20, which he released in February.

The order directed the State Department and Pentagon to report on whether countries receiving American arms are using them to break international law — for instance, through attacks that disproportionately harm civilians — and if those countries are blocking U.S. humanitarian aid. If U.S. officials confirm those conditions, the findings could trigger U.S. policies and legislation that bar weapons for countries taking such steps.

On May 10, the administration released its NSM-20 probe of Israel’s operation in Gaza. The assessment said it was “reasonable” to believe Israel had used American weapons in violation of international and U.S. standards for shielding civilians as its campaign in Gaza decimated the strip and killed tens of thousands of Palestinians. But the report downplayed Israel’s extensive restrictions on aid for Gaza and called Israeli assurances to respect international and U.S. law “credible” — prompting widespread criticism. Four months later, the Tuesday letter says a new assessment is essential.

“In the months since the NSM-20 report, the humanitarian catastrophe in Gaza has only worsened — yet your administration’s policy of virtually unconditional military support for the Israeli government continues,” reads the message. “NSM-20 clearly provides for the reconsideration of assurances the credibility or reliability of which has been ‘called into question.’ We urge an immediate, public review of Israel’s compliance with NSM-20.”

The timing of the call is significant. On Monday, Britain announced it would stop sending Israel 30 types of military supplies, including parts for jets and drones, because U.K. officials had concluded the equipment could be used to break international humanitarian law. The determination by the U.S.’s closest foreign ally could boost scrutiny of whether the Biden administration is accurately investigating Israel’s adherence to the global standards governing warfare.

The office of Israeli Prime Minister Benjamin Netanyahu called the British step “shameful” and claimed Israel “is comporting fully with international law.”

Meanwhile, Netanyahu is challenging U.S.-led efforts to reach a deal for a cease-fire in Gaza and the release of hostages captured in the Oct. 7 attack, even after six hostages, including Israeli-American Hersh Goldberg-Polin, were found dead on Sunday. Netanyahu’s actions suggest that without more pressure from the U.S., Israel’s main backer, the fighting — and continued seeming violations of American and international law — will continue.

Another factor will be introduced when lawmakers return to Capitol Hill later this month. Many Democrats in both chambers of Congress have challenged the flow of U.S. weapons to Israel, saying Biden should limit exports to force Israel to limit harm to civilians, permit more aid into Gaza and demonstrate it is upholding American and international laws. In the coming weeks, Sen. Bernie Sanders (I-Vt.) is expected to force a Senate vote on the matter, using a special legislative procedure to urge his colleagues to reject the Biden administration’s recently announced plan to send Israel an additional $20 billion in U.S. military equipment.

In the Tuesday letter, advocates for a change in Biden’s policy highlight research showing Israeli conduct is out of step with U.S. expectations, with a particular focus on developments since the NSM report was issued.

The amount of relief aid entering Gaza has plummeted since Israel took full control of the territory’s borders in May by capturing its southern boundary with Egypt, while aid workers “routinely come under fire” and 96% of the region’s residents lack sufficient food, the message notes. It adds that watchdogs and news outlets have tied Israeli strikes that killed dozens of Palestinians to U.S.-provided bombs, while rights groups have accused Israeli authorities of severely mistreating Palestinians who they have detained.

American officials could be putting themselves in legal jeopardy, per the letter, since they are aware of the pattern of alleged Israeli violations of international law and because of moves by international bodies, like the International Court of Justice, which in July directed governments not to assist Israel’s occupation of Palestinian territories, including Gaza, and the International Criminal Court, which is considering issuing warrants for the arrest of Netanyahu and his defense minister.

Human Rights Watch and Amnesty International, two of the statement’s signatories, publicly warned of U.S. government personnel’s liability last month.

The Biden “administration’s arming of the Israeli government has been and continues to be shockingly out of step with the realities of civilian harm and suffering in Gaza,” the message reads.