Obama and Netanyahu during a meeting at the White House, Nov. 2015 (Reuters)

WASHINGTON — The United States and Israel have reached final agreement on a record new package of at least $38 billion in U.S. military aid and the 10-year pact is expected to be signed this week, sources close to the matter told Reuters on Tuesday.

The deal will represent the biggest pledge of U.S. military assistance made to any country but also involves major concessions granted by Israeli Prime Minister Benjamin Netanyahu, according to officials on both sides.

Those include Israel’s agreement not to seek additional funds from Congress beyond what will be guaranteed annually in the new package, and also to phase out a special arrangement that has allowed Israel to spend part of its U.S. aid on its own defense industry instead of on American-made weapons, the officials said.

Israel’s chief negotiator, Jacob Nagel, acting head of Netanyahu’s national security council, arrived in Washington overnight in preparation for a signing ceremony with U.S. National Security Adviser Susan Rice, according to one source familiar with the matter.

Nearly 10 months of drawn-out aid negotiations have underscored continuing friction between President Barack Obama and Netanyahu over last year’s U.S.-led nuclear deal with Iran, Israel’s arch-foe. The United States and Israel have also been at odds over the Palestinians.

But the right-wing Israeli leader decided it would be best to forge a new arrangement with Obama, who leaves office in January, rather than hoping for better terms from the next U.S. administration, according to officials on both sides.

A deal now allows him to avoid uncertainties surrounding the next president, whether Democrat Hillary Clinton or Republican Donald Trump, and to give Israel’s defense establishment the ability to plan ahead.

Obama’s aides want a new deal before his presidency ends, seeing it as an important part of his legacy. Republican critics accuse him of not being attentive enough to Israel’s security, which the White House strongly denies.

Israel has long been a major recipient of U.S. aid, mostly in the form of military assistance.

The 10-year aid packages underpin Washington’s congressionally mandated requirement to help maintain Israel’s “qualitative military edge” in the region.

The deal, known as a memorandum of understanding, or MOU, calls for at least $3.8 billion a year in aid, up from $3.1 billion annually under the current pact, which expires in 2018, officials say. Netanyahu had originally sought upwards of $4.5 billion a year.

The new package for the first time will incorporate money for Israeli missile defense, which until now has been funded ad hoc by Congress. U.S. lawmakers have in recent years given Israel up to $600 million in annual discretionary funds for this purpose.

Officials say Israel has agreed not to lobby Congress for additional missile defense funds during the life of the new MOU, a pledge expected to be made in a side letter or annex to the agreement. But the wording is likely to be flexible enough to allow exceptions in case of a war or other major crisis.

Barring a last-minute snag, the new agreement is expected to be officially rolled out this week, one source close to the matter said. Another source familiar with the negotiations confirmed that the signing would be “in the coming days.”