The move by a House Armed Services subcommittee far exceeds previous U.S. funding for the Iron Dome system, developed by Rafael Advanced Defense Systems to counter short-range missiles and rockets.
The $680 million, slated as part of the U.S. budget for fiscal 2013, will be in addition to the record $3.1 billion in U.S. military aid to Israel this year and some $100 million in U.S. support for medium- and long-range missile defense systems already pledged.
The administration of U.S. President Barack Obama provided $205 million for Iron Dome in fiscal 2011.
Israel had earlier sought $700 million from Washington to pay for four Iron Dome batteries to reinforce three batteries already deployed.
Two are operational in the Negev Desert of southern Israel to counter rockets fired by Palestinian militants in the Hamas-ruled Gaza Strip. The third was recently deployed near Tel Aviv amid indications that the Palestinians were extending the range of their short-range rockets to reach the large urban area around Israel's financial center.
Israel's military command says that at least 20 batteries will be needed to provide effective nationwide defense against short-range missile attack from the Gaza Strip in the south and Lebanon in the north.
And that doesn't take into consideration the cost of production and operational use of other systems, such as the high-altitude Arrow, built by Israel Aerospace Industries and the Boeing Co. of the United States, and the mid-level David Sling developed by Rafael.
So, being election year, it's likely there will be further large-scale funding for Israel's missile defense shield in the months ahead unless the Obama administration can make significant headway with talks with Iran scheduled to start May 23 in Baghdad to defuse the current confrontation in the Persian Gulf.
Netanyahu's government says Iron Dome, first deployed in the south in March 2011, was able to shoot down 90 percent of the rockets it engaged in a recent sharp flare-up with Gaza.
The system is capable of distinguishing between rockets likely to hit populated areas and those that won't, and is designed to concentrate on the former.
Military sources say that Iron Dome's success rate was probably close to 70-75 percent.
But the government, faced with the threat of unprecedented bombardment of Israeli cities by everything from ballistic missiles to short-range unguided rockets by Iran, Syria, the Palestinians and the Iranian-backed Hezbollah in Lebanon, has been seeking to reassure the country's population of 7.3 million that it's capable of defending the home front against a sustained missile barrage.
Israel's supporters in the U.S. Congress have in recent weeks intensified efforts to secure extra U.S. funding for the multi-layered missile defense shield Netanyahu's rightwing coalition is pushing to create to counter the feared onslaught, the like of which Israel has not endured since its creation in 1948.
With Obama facing a tough fight to secure re-election in November, he is unlikely to jeopardize the Jewish vote by denying funding to Israel at a time when the Middle East's war drums are beating, much of it by Netanyahu's hawkish administration.
"Iron Dome's a gamechanger, saving innocent lives and protecting Israelis," declared U.S. Rep. Howard Berman, D-Calif., the ranking member of the House Foreign Affairs Committee.
"Securing additional funding to deploy additional Iron Dome batteries is an Israeli necessity, an American priority and a strategic imperative."
The funds for Iron Dome have yet to be approved by the full House Armed Services Committee in May and then the full House and Senate before going Obama for final approval.
There seems little doubt that will be forthcoming. The Iron Dome Support Act, designed to secure whatever backing Israel requests for Iron Dome, was introduced in the Congress in March by Berman and Foreign Affairs Committee chairwoman Rep. Ileana Ros-Lehtinen, R-Fla.
Reps Gary Ackerman, D-N.Y., ranking member of the Middle East and South Asia subcommittee; Steve Chabot, R-Ohio, chairman of that subcommittee; David Cicilline, D-R.I.; Ann Marie Buerkle, R-N.Y., signed on as co-sponsors.