Joe Biden is committing “an apparent violation of U.S. law” by continuing to send military assistance to Israel while the nation blocks American aid for Gaza, 25 prominent humanitarian and human rights organizations argued in a Tuesday letter to the U.S. president.

In the letter, shared exclusively with HuffPost, the groups cited Biden’s decisions in recent days to airdrop aid into Gaza and launch a complex plan to build a floating pier to provide food to people there, some of whom have begun dying of malnutrition and dehydration, as an acknowledgment that Israel is impeding the delivery of crucial U.S. supplies.

“Both efforts are the latest implicit recognition of Israel’s severe restrictions on humanitarian access amid extraordinary human suffering,” reads the message, which was delivered to the U.S. National Security Council. “Your administration has now publicly recognized what humanitarian organizations have reported for months: that the government of Israel is obstructing the delivery of humanitarian aid to starving Palestinians.”

The letter came after eight senators also sent Biden a missive saying Netanyahu is breaching laws governing U.S. military aid.

At question is Section 620I of the Foreign Assistance Act, which says that presidents cannot provide military aid to foreign countries if they know those nations are barring the delivery of U.S. humanitarian relief. In the letter, the groups argued that Biden is violating the law by refusing to end “unconditional arms transfers” and other support for Israel’s ongoing deadly offensive in Gaza, which has so far killed more than 30,000 Palestinians, per local authorities.

The Biden administration has repeatedly said that it and Israel are abiding by U.S. laws in their actions in Gaza, and challenged demands for probes of Israeli actions and potential U.S. complicity in war crimes.

The Tuesday statement represents a striking accusation from well-respected groups, ranging from rights watchdogs like Amnesty International and the Center for Civilians in Conflict, or CIVIC, to major aid bodies such as Oxfam America, the Norwegian Refugee Council and Refugees International. It will likely intensify conversations about the aid statute among key policymakers — as well as frustration among critics of Biden’s Gaza policy.

Sens. Chris Van Hollen (D-Md.) and Bernie Sanders (I-Vt.) and Rep. Jim McGovern (D-Mass.) have recently urged Biden to invoke the law to force Israel to change its aid approach for fear of losing irreplaceable U.S. military backing.

“About three weeks ago, I asked senior State Department officials to tell me why this law …has not been applied,” Van Hollen said on the Senate floor on March 5. “I haven’t gotten an answer.”

In February, Sanders and 17 Democratic senators supported legislation from Van Hollen that cited Section 620I and would have required Biden to secure assurances from partner countries, like Israel, that they will fully cooperate with U.S. attempts to distribute aid globally. The Biden administration drew on Van Hollen’s bill to roll out a new policy governing arms transfers to nations including Israel. But analysts say it will do little to help Gaza today and could be an “empty promise” in the long run.

Well-known former Sen. Patrick Leahy (D-Vt.) last week told The Independent that he believes current U.S. aid for Israel is violating a different law he championed barring assistance for military units committing major human rights abuses.

The prospect of applying Section 620I during international conflicts has previously arisen twice — but it has never been fully implemented.

Congress passed the law in the 1990s, when Turkey was restricting humanitarian assistance to Armenia as it feuded with Azerbaijan, a Turkish ally. Legislators pushed for Section 620I to be applied to Turkey — a member of NATO, which works closely with the U.S. military — and then-President Bill Clinton’s administration acknowledged that the statute was relevant, but issued a waiver to maintain military aid despite Turkish aid interference, as Brian Finucane, a former State Department lawyer, noted on X.

And in 2017, under scrutiny from Sen. Todd Young (R-Ind.), then-State Department legal adviser nominee Jennifer Newstead said that the law could apply to Saudi Arabia, which was receiving U.S. military assistance as it waged war in Yemen and limited how much aid entered that country. Newstead ultimately served as State’s top lawyer from January 2018 to April 2019.

But Finucane added in a later post that the Biden administration may be loath to even acknowledge a violation while the International Court of Justice is still weighing a case on whether Israel is committing genocide in Gaza; the U.S. could end up strengthening a suit that might implicate U.S. officials who are enabling the campaign. HuffPost has previously revealed that several U.S. government agencies are tracking whether Israel’s Gaza policy involves violations of international and U.S. law.

Regardless of the Biden administration’s willingness to acknowledge the law, clearly worsening conditions in the Palestinian enclave mean it cannot be ignored for good, activists and analysts argue.

“Restrictions are not isolated instances but the policy of the government of Israel,” the Tuesday letter tells Biden, citing repeated statements by Israeli Prime Minister Benjamin Netanyahu, as well as Israel’s denials of humanitarian requests and attacks on civilians seeking aid.

“During your own State of the Union address, you implicitly acknowledged that Israel was using humanitarian aid as a bargaining chip,” the message continues. “We demand that you urgently comply with U.S. law, end U.S. support for catastrophic human suffering in Gaza, and use your leverage to protect civilians and ensure the impartial provision of humanitarian assistance.”

The Biden administration has said that Israeli ministers in Netanyahu’s government are deliberately preventing aid from getting to Gaza.

Asked by reporters on March 6 if that assessment meant the U.S. believes Section 620I should be triggered, State Department spokesperson Matthew Miller said, “That’s not something that I’ve spent a lot of time looking at, but we are always engaged with Israel, as we are with all countries, about their need to fulfill all U.S. statutory requirements, and we have not made an assessment that Israel is in breach of any such statutory requirements at this time.”

Oxfam and Human Rights Watch have said that Israel is deliberately starving civilians as part of its military strategy in what would represent a war crime. Annie Shiel, the U.S. advocacy director at CIVIC and an organizer of the Tuesday letter, told HuffPost that Biden’s current approach of unconditional support for the Israeli strategy and “insufficient” U.S. aid amounts to “a green light for more devastation.”

The president has ratcheted up criticism of Netanyahu, saying in an interview aired on March 9 that the prime minister’s military campaign is “hurting Israel more than helping.” Yet he reiterated that he does not envision cutting off weapons for the country, mentioning Israel’s right to defend itself and its Iron Dome missile defense system.

U.S. supplies for the Iron Dome system are not transferred under the law that contains Section 620I and covers most American military exports, so Biden would not risk that shield if he were to enforce the statute over Israel’s handling of humanitarian aid, according to John Ramming Chappell, an advocacy and legal fellow at CIVIC.

“The Biden administration has always been bound to comply with Section 620I — but since it has not done so to date, congressional pressure is also vital to press President Biden to immediately obey the law and ensure lifesaving aid reaches civilians living on the brink of famine,” Chappell told HuffPost.

Since Israel launched its U.S.-backed incursion following an Oct. 7 attack led by the Gaza-based Palestinian faction Hamas that killed around 1,200 people in Israel, its tactics have spurred worldwide horror. Israeli restrictions on aid — affecting both the northern section of the region, which Israel has controlled for months, and the southern town of Rafah, which it plans to capture next and where more than 1 million displaced Palestinians are sheltering — have led to mass starvation and public health crises.

U.S.-backed Israeli attacks have also killed multiple aid workers. On March 8, an Israeli airstrike killed Mousa Shawwa, an employee of the humanitarian group Anera, which signed on to the Tuesday letter to Biden.

The situation has sparked immense alarm and outrage among professional humanitarian groups, many of whom blasted Biden’s recent new proposals for Gaza.

“Oxfam does not support U.S. airdrops to Gaza, which would mostly serve to relieve the guilty consciences of senior U.S. officials,” Scott Paul of Oxfam America recently wrote on X.