Updated at 12:12 p.m.

As part of a 10-year U.S.-Israel security aid agreement, the Israeli government has signed a letter promising to give back any additional money that Congress appropriates, effectively preventing Congress from giving Israel any more money than President Obama wants it to have.

The White House will sign today a new 10-year Memorandum of Understanding (MOU) with Israel that would increase U.S.-Israel security aid from $3.1 billion a year to $3.3 billion, starting in 2018. The deal would also include, for the first time, $500 million of annual missile defense funding, bringing the annual total to $3.8 billion. But Congress, in its appropriations bill, has been planning to give Israel $3.4 billion, plus $600 million for missile defense, in 2017.

The Obama administration had been holding off on signing the deal until Congress reduced its funding to meet Obama’s proposed levels, but Congress refused to do so. So the administration pressed Israel to promise not to lobby for additional money. Israel agreed, but that wasn’t enough.

In an unprecedented arrangement, the White House and the Israeli government have found a way to prevent Congress from increasing U.S. aid for 2017 and 2018. The Israeli government has signed a letter promising to return any money given by Congress above the MOU levels for those two years.

Sen. Lindsey Graham (R-S.C.), chairman of the Senate appropriations subcommittee that manages the foreign affairs budget, told me he was informed of the unusual arrangement by the Israelis and White House Chief of Staff Denis McDonough.

“As part of this deal, Israel has signed a letter to this administration saying they will not accept the money above the MOU amount and they would return it,” Graham said. “I said, ‘I think y’all have lost your mind. You’ve been trying to get a foreign government to help you take over the appropriations process.’ ”

Administration sources confirmed to me that the arrangement exists and said that the Israeli government had “volunteered” to give back any money above the deal’s limits. Graham said the Israelis told him they wrote the letter promising to return any extra funds.

“You know the White House pressured them into writing that letter,” Graham said. “It is a level of antagonism against Israel that I can’t understand.”

Graham pointed out that Congress regularly increases foreign aid above the levels in MOUs when dealing with other countries. For example, Congress increased foreign aid to Jordan above its $1 billion annual allotment last year in light of that country’s refugee crisis.

A senior Obama administration official told me that keeping the levels of aid equal to the MOU was important because a critical component of the MOU is that it provides predictability for planning purposes.

“In this context, changes to funding levels under the MOU in either direction are a threat to the integrity of the MOU, impeding planning and undermining confidence in future appropriations,” the official said.

The official pointed to a July 25 statement issued by the office of Israeli Prime Minister Benjamin Netanyahu that said “it is not in Israel’s interest for there to be any changes to the fixed annual MOU levels” and pledging that Israel is not seeking additional funding.

“Israel understands that, once the precedent of changes to MOU levels is established, it would create uncertainty that is undesirable for both sides,” the official said. “Ultimately, the United States fully agrees with Israel on the need to respect the integrity of the MOU and avoid changing the appropriation level in any given year. It is for this reason that we also oppose any appropriation greater or less than those specified in the MOU.”

But even former Obama administration officials have stated that it’s actually standard for Congress to retain its right to appropriate foreign aid at levels it alone determines. Tamara Cofman Wittes, a Brookings Institution scholar and former Middle East official in the Obama administration, tweeted this week that Congress still has the right to appropriate whatever it wants.

Wittes pointed out that the last U.S.-Israel MOU made clear that the agreement was “subject to the appropriation and availability of funds for these purposes,” meaning that Congress still played a role.

Graham is planning to take his fight over what he sees as an executive power grab to the Senate floor. He is going to propose a new and additional $1.5 billion supplemental aid bill for Israel next year, and he predicts Republicans and Democrats will support it.

Why Israel would agree to both not seek and not accept any additional funding from Congress is unclear. What is clear is that the White House has effectively taken Congress out of the Israel aid game for at least two years. If Israel’s security needs go up between now and then, it will have to look outside the United States for help.

The office of House Speaker Paul Ryan (R-Wis.) issued a statement Wednesday reaffirming Congress’s right to appropriate security aid to Israel at its own discretion, regardless of the levels in the MOU.

“Congress was not consulted during the negotiation of the MOU,” said Ryan’s press secretary AshLee Strong. “We will continue to appropriate the funds that we determine are necessary to meet the needs of our shared security interests in the Middle East.”