The increase in the U.S. arsenal in the Jewish state now under way, reported by the Washington-based Defense News weekly, will reinforce support for Israel by the administration of U.S. President Barack Obama in the confrontation with Iran over its contentious nuclear program.
That commitment was evidenced by a two-week joint air-defense exercise, Juniper Cobra 10, by U.S. and Israeli missile forces in October-November 2009, the largest exercise ever held by the two allies.
Some 1,500 U.S. personnel, along with 17 warships from the 6th Fleet, participated in countering simulated attacks by ballistic, medium-range and short-range missiles and rockets on Israel.
These efforts are also seen as an attempt by the Obama administration to reassure Israel that the Americans will support them in a confrontation with Iran -- though not necessarily with combat forces -- and to encourage the Jewish state not to launch unilateral air and missile strikes at Iran's nuclear facilities.
In 2008 the Pentagon also installed a strategic long-range X-band radar system at Nevatim air base in the Negev Desert south of Tel Aviv. It can detect incoming missiles from hundreds of miles away.
At the time Juniper Cobra was being held, there were reports that the Americans would leave several Patriot PAC-3 air-defense systems behind once the maneuvers ended.
It is not clear whether they are included in the reported increase in U.S. stockpiles.
The expansion of these stockpiles emerged amid a heightening of tension with Iran, as a U.S.-led dialogue with Tehran appeared to flounder after four months of tortuous negotiations that have failed to produce any concrete agreement by Iran to curb its nuclear program.
The Israelis view a nuclear-armed Iran as an existential threat and have said they will launch unilateral military strikes against the Islamic Republic if it believes Tehran is close to acquiring nuclear weapons.
Israel's leadership believes Iran is using the talks to buy time to push forward with its program and that 2010 will be the year of decision regarding military action.
This has led to reviews of Israel's strategic position in the event of hostilities.
Any conflict that erupts will probably not be a swift exchange of airstrikes and missile salvoes, as many expect, but will probably drag on for weeks or months.
According Amos Harel, an analyst with the liberal Israeli daily Haaretz, a key Israeli Defense Ministry researcher, Moshe Vered, has concluded that "the ideology of the Iranian regime will dictate a prolonged war."
Harel wrote that Vered argues that the length of that war "will be measured in years, not in weeks or days" because of the Shiite perception "by which one must fight and sacrifice for the sake of justice and to correct wrongs to Islam and to Muslims."
"This outlook sees Israel's existence as a wrong that must be corrected for the sake of world redemption. …
"Iran's willingness to sacrifice many victims for a long period of time in a conflict with Israel will dictate a prolonged war between the two states that will be difficult to end."
If that is the case, U.S. military stockpiles in Israel may be increased further.
Israeli forces ran critically short of ordnance and military equipment in the October 1973 war when the Jewish state was attacked by Egypt and Syria and was nearly overwhelmed.
Only a major U.S. airlift ordered by President Richard Nixon saved the day.
In the 34-day 2006 war with Hezbollah, Israeli stocks of air force bombs and artillery ammunition were seriously depleted, almost to what the army deemed a critical level.
According to Defense News, the current buildup "is the final phase of a process that began over a year ago to determine the type and amount of U.S. weapons and ammunition to be stored in Israel."
That, it added, was "part of an overarching American effort to stockpile weapons in areas in which its army may need to operate, while allowing American allies to make use of the ordnance in emergencies."
The United States began stockpiling $100 million in military equipment in Israel in 1990.