The Obama administration reached a deal with Israel to provide the country with $3.8 billion a year in military aid over a decade, according to people familiar with the agreement, a 23% increase over current levels.
The aid package, totaling $38 billion, is set to be formally announced Wednesday by U.S. and Israeli officials at a signing ceremony at the State Department.
The new memorandum of understanding includes $500 million for missile defense. It increases U.S. aid to Israel from the current $3.1 billion a year to $3.8 billion annually from 2019 to 2028, after the current agreement expires.
Israeli Prime Minister Benjamin Netanyahu's office issued a brief statement Tuesday saying the two governments had reached a deal that "constitutes the single largest pledge of assistance in U.S. history."
Reaction among U.S. lawmakers was mixed, with some welcoming the agreement while others decried it as insufficient given the extent of threats facing Israel.
"As Israel faces worsening threats around the world, this [memorandum of understanding] demonstrates that the United States will stand with Israel," Rep. Eliot Engel of New York, the top Democrat on the House Committee on Foreign Affairs, said in a statement. "I'm confident that support in Congress for this agreement-like support for Israel in general-will be strong and bipartisan."
Sen. Lindsey Graham (R., S.C.) criticized the new agreement as inadequate, providing $300 million a year below levels that have met with approval by lawmakers and insufficient support for missile defense.
"Congress has an independent duty to make a decision about the proper level of support for Israel or our other allies," Mr. Graham said in a statement.
The U.S. has long provided Israel with a substantial annual military aid package, which is intended to help the country maintain a military edge over its neighbors and is often touted as the bedrock of the relationship.
President Barack Obama set reaching a new agreement with Israel before he leaves office in January as a priority, and his administration spent months in negotiations.
Those talks appeared at times in jeopardy. The relationship between Messrs. Obama and Netanyahu soured over differences on the Iran nuclear deal, and in March the Israeli leader abruptly canceled a meeting with the president because of apparent disagreements in negotiations on the military-aid package.
Despite the delays and the tension between the Obama and Netanyahu governments, the agreement reflects a continuing security relationship, experts said.
"The package demonstrates that despite all the ups and downs in the U.S.-Israeli relationship, the security piece continues," said Aaron David Miller, a vice president at the Woodrow Wilson Center for Scholars in Washington, D.C., and a former Israeli-Palestinian peace negotiator.
In recent years, the U.S. has invested millions of dollars in many of Israel's most-effective deterrents, including the Iron Dome missile defense system that has stymied the threat short-range rocket attacks from enemies such as Lebanese militant and political group Hezbollah and Islamist movement Hamas.
The U.S. has provided more than $40 million to Israel to create anti-tunneling technology to blunt attempts by Hamas to enter Israel underground from the Palestinian territories. Israel's military in April found a reinforced-concrete tunnel from the Gaza Strip, an area Hamas has controlled since Israel ended its occupation in 2005.
By the end of this year, Israel's air force will also take delivery of the first F-35 Joint Strike Fighter.
"We take Israel's security extremely seriously," the U.S. ambassador to Israel Dan Shapiro said in a speech on Sunday laying out the areas of support.
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