The United States is the primary source of Israel's far superior arsenal. For more than 30 years, Israel had been the largest recipient of U.S. foreign assistance and since 1985 Jerusalem has received about $3 billion in military and economic aid each year from Washington. U.S. aid accounts for more than 20% of Israel's total defense budget.
Over the past decade, the United States has transferred more than $17 billion in military aid to this country of just under 7 million people.
Israel is one of the United States' largest arms importers. Between 1996 and 2005 (the last year for which full data is available), Israel took delivery of $10.19 billion in U.S. weaponry and military equipment, including more than $8.58 billion through the Foreign Military Sales program, and another $1.61 billion in Direct Commercial Sales
During the Bush administration, from 2001 to 2005, Israel received $10.5 billion in Foreign Military Financing—the Pentagon's biggest military aid program—and $6.3 billion in U.S. arms deliveries. The aid figure is larger than the arms transfer figure because it includes financing for major arms agreements for which the equipment has yet to be fully delivered. The most prominent of these deals is a $4.5 billion sale of 102 Lockheed Martin F-16s to Israel.
Source: Frida Berrigan and William D. Hartung http://www.fpif.org/fpiftxt/3387