There is deepening concern in Israel that U.S. sequestration signals cuts of up to $500 million in U.S. military aid in the months ahead, slowing a crucial missile defense program at a time when sanctions-battered Iran could strike.

"While exact figures pertaining to any sequestration-related cuts remain shrouded in the fog of behind-the-scenes negotiations and much political grandstanding, a full implementation of sequestration would mean significant reductions in U.S. military assistance to Israel, including funding for joint missile defense programs and the Iron Dome short-range, anti-rocket system," The Times of Israel observed.

Sequestration is a program of across-the-board cuts in U.S. spending aimed at slashing the annual federal deficit estimated at $900 billion and cutting the nation's $16.6 trillion debt.

This is widely expected to have a major effect in Israel, which benefits hugely from U.S. economic and military aid -- currently some $3.1 billion a year -- as well as loans, loan guarantees, grants and "discretionary" handouts that have totaled around $80 billion in recent years.

Some estimates state that Israel could lose around $263.5 million of the $3.1 billion annual aid package over the next year.

Israel's Globes business daily observed there's mounting concern that U.S. aid this year for the Jewish state's multilayered missile defense program known as "Homa" -- the Wall -- "will not be reduced proportionately, but will be eliminated altogether."

Israel is to receive $211 million in U.S. aid this year to buy more batteries of the Iron Dome system, which is designed to shoot down missiles and rockets with ranges of 2-140 miles, to add to the four batteries already deployed.

The $211 million is part of a four-year Iron Dome aid package totaling $680 million.

Israeli military chiefs estimate they need as many as 20 batteries of Iron Dome, developed by Israel's Rafael Advanced Defense Systems, to provide effective cover for the whole country against such weapons held by Hezbollah in Lebanon, Hamas in the Gaza Strip and Syria.

Another $268 million in U.S. aid this year is designated for the Arrow-3 system, designed to intercept ballistic missiles in the final stages of their trajectories outside Earth's atmosphere, and the mid-range David's Sling system.

Arrow was developed and is produced by state-owned Israel Aerospace Industries and the U.S. Boeing Co. David's Sling, also known as Magic Wand, is under development by Rafael and the Raytheon Co. of the United States.

Arrow-3 successfully underwent its first test-flight into space Feb. 25 and is expected to be deployed in 2016 to augment Arrow-2, which is currently in service and operates at a lower altitude.

"If the aid packages for missile systems is eliminated, and the reduction in current military aid is added, Israel will lose almost $750 million in U.S. aid in the 2013 fiscal year," Globes reported.

"If the budget cut for the missile programs is proportional, Israel will lose just over $300 million in military aid."

Other estimates cite $500 million, with the impact of the U.S. cuts magnified by planned cutbacks in Israel's defense budget.

Israeli planners had hoped the powerful Israel lobby in Washington would be able to minimize the effects of sequestration on such a key ally.

But Globes observed that even though "Israel's friends in Congress are well aware of Israel's distress ... their hands are tied ... The sequestration allows no exceptions.

"Moreover, under the current political reality, members of Congress cannot be seen to act on behalf of another country when the sequestration will devastate tens of millions of Americans."

The start of sequestration coincides with the annual policy conference of the American Israel Public Affairs Committee in Washington, which has lobbied against the cuts.

It's expected to discuss ways of minimizing the cuts and to focus on the danger posed by Iran's contentious nuclear program and its drive to develop intermediate range ballistic missiles like the Shebab-3 and the Sejjil-2 that Israel sees as an existential threat.

Israel is becoming increasingly isolated internationally because of its failure to move the disintegrating peace process forward. Relations with Washington are strained.

AIPAC President Michael Kassen warned Sunday that "the growing allure of isolationism" in U.S. politics threatens U.S.-Israeli relations and is "extremely dangerous" for Israel's security.