They cited multiple evacuation orders that had crammed 1.7 million people into a narrow strip placing them at “high risk of lethal contagion,” closing crossings into Gaza to aid deliveries, delaying trucks carrying humanitarian supplies including U.S-funded perishable goods, blocking of commercial imports and cutting off 400,000 people in northern Gaza by “denying or impeding” 90% of humanitarian movements to assist people there in September.

The letter, reported by Axios, states that the U.S. departments of State and Defense are required by law to continually assess whether Israel is facilitating, and not arbitrarily denying, restricting or otherwise impeding, directly or indirectly, the uninterrupted delivery of U.S. humanitarian assistance and U.S. government-supported international assistance efforts.

“The Department of State will need to conduct a similar assessment under Section 620I of the Foreign Assistance Act in order to provide additional Foreign Military Financing assistance to Israel,” the letter says.

It also references a National Security Memo signed by U.S. President Joe Biden in February requiring that states in receipt of U.S. military aid that are engaged in a military conflict allow the free transfer of U.S.-supported humanitarian aid without interruption.

The letter demands that Israel initiate a surge of humanitarian assistance of all types throughout Gaza ahead of the oncoming winter allowing in at least 350 trucks daily, ensure commercial and Jordan Armed Forces corridors operate fully and continuously by waiving customs for the JAF and reinstating a daily minimum of 50-100 commercial trucks; and end the isolation of northern Gaza by halting forced evacuations and ensure continuous humanitarian access via northern crossings and from the south.

It says Israel must act immediately and within 30 days and that failure to demonstrate a sustained commitment to implementing and maintaining these measures “may have implications for U.S. policy under NSM 20 and relevant U.S. law.”

U.S. State Department spokesman Matthew Miller told a briefing Tuesday that the intention of the letter, which he stressed was a private diplomatic cable that was not meant to be put in the public domain, was to remind the Israeli government that there were “changes they need to make again to see the level of assistance making it into Gaza comes back up.”

“We are required to conduct assessments and find that recipients of U.S. military assistance do not arbitrarily deny or impede the provisioning of U.S. humanitarian assistance. That’s just the law. And we of course will follow the law,” said Miller.

But he refused to be drawn on what might be the upshot if Israel failed to comply saying he hoped it would not come to that because Israel would react by making the changes outlined in the letter.

“We have seen Israel make changes before, and when they make changes, humanitarian assistance can increase,” he said pointing to Israel’s work with humanitarian organizations in the past few months to implement a child polio mass vaccination program in Gaza.

“So we know that it’s possible to get humanitarian assistance into Gaza. We know it can be done. We know that the various logistical and bureaucratic obstacles can be surmounted, and so it is incumbent upon the Government of Israel to surmount those challenges and get assistance in.”

However, Miller categorically denied that the 30-day deadline was in any way linked to the U.S. presidential election, less than three weeks away, saying it was only reasonable to give the Israeli government an appropriate period of time to implement the changes.

Axios quoted an Israeli official as confirming the letter had been received and that it was being looked at by Israeli security officials.

“Israel takes this matter seriously and intends to address the concerns raised in this letter with our American counterparts,” said the official.

However, Israeli Prime Minister Benjamin Netanyahu lashed out against the warning from State and the Pentagon saying it was tantamount to an arms embargo, according to the BBC which also reported that Biden was facing criticism from Republicans on Capitol Hill.