That'll be the second time in a year that the Americans have stepped in to underwrite the system developed by Israel's Rafael Advanced Defense Systems. Iron Dome is the bottom layer of a planned four-tier, anti-missile defense system.
It's also on top of the $3 billion in military aid for Israel by the United States as well as billions more in loans and grants.
Meantime, the Israeli air force is scheduled to take delivery of an advanced model of the Arrow-2 missile interceptor in the next few weeks. Arrow, built by state-owned Israel Aerospace Industries and the U.S. Boeing Co., has been heavily subsidized by the United States for two decades.
The Iron Dome bill was put together by House of Representatives Republicans led by House Foreign Affairs Committee Chairwoman Ileana Ros-Lehtinen, R-Fla., and Armed Services Committee Chairman Howard McKeon, R-Calif.
They and other Republicans, diehard supporters or Israel, have rounded on the administration for seeking to cut back military aid to the Jewish state amid major cuts in U.S. defense spending.
They told Obama in a Feb. 14 letter: "We are deeply concerned that at a time of rising threats to our strongest ally in the Middle East, the administration is requesting record-low support for this vital defense cooperation program."
Obama is quarreling with Netanyahu over West Bank settlements and threats to attack Iran but he also faces a stiff re-election fight in November so it's not likely he'll oppose giving Israel another $680 million for Iron Dome through 2015, on top of the $205 million he authorized in fiscal 2011.
The bill's likely to come under scrutiny this week when the House Armed Services Committee begins putting together the 2013 Defense Authorization Act.
Israel's Defense Ministry, beset by controversial cuts in Israel's defense budget and concerns of new conflict in the Middle East, is grappling with the problem of funding costly plans to build a multilayered shield against an unprecedented missile and rocket bombardment.
Ministry sources say, for instance, that $3.9 billion is needed to produce more batteries of the long-range, high-altitude Arrow system.
Israeli officials said in early April that the ministry is seeking $700 million from the United States to pay for at least four additional Iron Dome batteries to reinforce the three already deployed.
That more or less tallies with the $680 million now being sought by Republicans in Congress.
In March a bipartisan group introduced the Iron Dome Support Act in Congress authorizing the administration to provide more funds to Israel to extend the air-defense system.
Another reason why the administration is expected to heed the Republicans' request is to encourage Netanyahu to heed U.S. entreaties to hold off an assault on Iran, which Washington fears would trigger a regional war.
Israel's Ynet Web site, the online service of the mass-circulation Yediot Ahronot daily, acknowledged in April that "the U.S. Congress and administration's apparent willingness to allocate the funds may be seen as an attempt to incentivize Israel to delay its decision vis-a-vis a military strike on Iranian nuclear facilities."
The Arrow, designed to destroy ballistic missiles at high altitudes, has also been heavily funded by the United States since it began development in May 1986. The program's projected cost in 1986 was $1.6 billion but by 2007 it had cost $2.4 billion, with up to 80 percent provided by Washington. Israel's contribution was $65 million a year.
The upgraded interceptor will contain new software to increase its accuracy against long-range missiles like Iran's Shehab-3b and Sejjil 2, and Syria's Scud-Ds.
Arrow-3, the next model, is under development and is intended to intercept ballistic missiles outside Earth's atmosphere and could serve as an anti-satellite weapon.
The first Arrow battery was deployed south of Tel Aviv in 2000. A second battery is deployed in northern Israel.
Arrow-3 will comprise the top tier of Israel's anti-missile network, with Arrow 2 the next layer down. Below that will be David's Sling, being developed by Rafael to counter medium-range missiles.