Amid concerns about rising tensions in the Persian Gulf, a U.S. House of Representatives defense subcommittee has approved nearly $1 billion for Israel's anti-missile defense program, the highest single appropriation for the four-system project.

It includes the high-altitude Arrow 3 being developed by Israel Aerospace Industries and the Boeing Co. to destroy Iranian and Syrian ballistic missiles outside Earth's atmosphere.

The move by the Defense Appropriation subcommittee also covers the only missile defense system so far used in combat, Iron Dome, built by Rafael Advanced Defense Systems of Israel to counter rockets with a range of 3-40 miles.

The $680 million slated for that system, designed to intercept short-range missiles and rockets and the lower rung of the planned missile defense shield, got the green light from the subcommittee April 29.

"The total appropriation ... reflects not only U.S. representatives' consistent support for Israel, but also rising concern about the Israel-Iran confrontation, which is liable to expose Israel to missile strikes from Iran, Hezbollah and Hamas," Israel's Globes business daily reported Tuesday.

The subcommittee was scheduled to vote on a draft bill encompassing the $1 billion later Tuesday.

The funding is separate from the $3.1 billion in military aid Israel gets from the United States annually.

So if the appropriation goes through, as expected, the Jewish state will be receiving a record $4 billion in military aid in fiscal 2013.

The House bill lists $74.69 million for the Arrow-3, "the upper-tier component to the Israeli Missile Defense Architecture."

The Arrow System Improvement Program, including the development of a long-range, ground and airborne, detection suite, will get $44.36 million, Globes reported.

This program involves upgrading the Arrow-2 missiles currently deployed to Block 4 capability, increasing their accuracy and destructive power.

Arrow became operational in 2000, with two batteries deployed in northern Israel and south of Tel Aviv.

A third missile defense system, David's Sling, is down to receive $149.68 million. This system, still under development by Rafael and the U.S. Raytheon Co., is designed to intercept missiles with a range of 24-150 miles.

This system, also known as Magic Wand, is expected to become operational in 2013 and to eventually replace Israel's Raytheon-built Patriot Advanced Capability-3 air-defense missiles.

The allocations for Arrow 3, the Arrow Improvement Program and David's Sling total $268.7 million, compared with the $235 million appropriated for them in fiscal 2012.

U.S. President Barack Obama authorized $205 million for Iron Dome in fiscal 2011.

The allocations for that system are aimed at funding the purchase of up to 15-20 batteries of the short-range defense system that Israeli military chiefs say are needed to provide anti-missile cover for the entire Jewish state.

Only three batteries have been deployed since Iron Dome was declared combat operational in March 2011.

These are deployed primarily to cover the southern cities of Beersheba, Ashkelon and Ashdod, which are within range of Palestinian rockets fired from the Gaza Strip.

But Palestinian militants now have unguided Russian-built Grad 122mm rockets capable of hitting the southern fringe of the major conurbation around Tel Aviv, Israel's commercial and financial hub.

Iron Dome, a mobile system that can distinguish between rockets that will hit populated areas and those that won't, ran up an impressive rate of kills in recent clashes in southern Israel.

Military officials claimed it destroyed 90 percent of the rockets it engaged, but informed sources say the figure was closer to 70 percent.

Iron Dome is the first system of its kind in the world to be deployed, but questions remain whether it would be able to meet the challenge of much heavier broadsides from Hezbollah in Lebanon.

During the monthlong 2006 war between Israel and Hezbollah, the conflict that taught the Jewish state the harsh lesson of just how vulnerable it was to mass missile attack, Hezbollah hammered northern Israel with 150-200 rockets a day.

These days, according to Israel intelligence, Hezbollah has in excess of 43,000 missiles and rockets, including long-range weapons capable of hitting anywhere in Israel.

Israeli military commanders warn that in any new conflict, Iran, Syria, Hezbollah and the Palestinians in Gaza could unleash 300-plus missiles and rockets a day over several weeks, with Tel Aviv and other cities facing sustained round-the-clock bombardment for several weeks.

That puts Israel's population centers on the front line for the first time since the state was created in 1948.