Israel has postponed final tests on its Iron Dome missile defense system, further delaying its deployment, as the outgoing chief of staff warns that Hezbollah could fire 400-600 missiles a day into the Jewish state if war erupts anew.

Iron Dome, built by state-owned Rafael Advanced Defense Systems to shoot down short-range rockets and missiles, had been slated for deployment with considerable fanfare in the summer.

But that was put back until November, supposedly to give more time for the air force to train crews on the complex system. Now officials say more test-firings have been scheduled and are expected to last several weeks.

Iron Dome, the bottom tier of a three-layer national air-defense shield, has been widely criticized inside and outside the military as being incapable of coping with mass salvos of projectiles fired by Hezbollah in Lebanon, Israel's northern neighbor, and Palestinian Hamas fighters in the Gaza Strip in the south.

The delays in declaring it operational, plans to keep the two batteries so far purchased by the military in storage rather than on the vulnerable borders, plus financing difficulties have done little to convince Israelis that the system will be able to defend them.

The U.S. Congress has approved President Barack Obama's request to provide $205 million for Israel to buy more Iron Dome batteries, each armed with 20 interceptors and equipped with multi-mission radars built by Israel Aerospace Industries.

The only component of the planned air defense shield in place is the long-range, high-altitude Arrow interceptor missile, which has been deployed since 2000. It is designed to shoot down Iran's ballistic missiles.

The third layer, known as David's Sling, is meant to counter medium-range missiles. It's under development by Rafael and isn't expected to be fielded until next year.

The concerns about whether these systems will be sufficient to cope with mass salvos of rockets fired by Hezbollah and Hamas, possibly joined by longer-range weapons from Syria and Iran, were deepened in December.

Israeli Maj. Gen Gadi Eisenkot, head of the Northern Command facing Hezbollah, declared that even though Israel's population centers are going to be key targets for missile attacks in any future war, the anti-missile defenses will be concentrated to protect military bases, "even if this means that citizens suffer discomfort."

Israel faces with a multi-front war if hostilities erupt in which the main threat to the nation will be massive bombardment by missiles and rockets on an unprecedented scale.

Hezbollah is reported to have built up an arsenal in excess of 40,000 missiles and rockets, hundreds of them capable of hitting anywhere in Israel, including the vast urbanized area around Tel Aviv, where 2 million people live.

For months, the nation's military leaders have been warning the population they face a potential firestorm, infinitely more devastating than the 4,000 short-range missiles Hezbollah unleashed against northern Israel in a 34-day war in 2006.

Casualties could run into the thousands if the air-defense network is overwhelmed, as many fear it will since Israel's powerful ground forces will be marginalized by the aerial threat.

According to U.S. diplomatic cables made available by WiliLeaks, and published Sunday in the Norwegian daily Aftenposten, Israel's intelligence service estimates Hezbollah could fire 400-600 missiles a day into Israel.

In the cables, dated November 2009, one official estimated that Tel Aviv would be hit by at least 100 missiles.

The outgoing chief of staff, Maj. Gen Gabi Ashkenazi, told U.S. officials visiting Tel Aviv that he was preparing for a "major war." He said Iran had more than 300 Shehab-3b ballistic missiles deployed, all capable of reaching Israel, which would have 10-12 minutes' warning once launches were detected.

"The rocket threat against Israel is more serious than ever," Ashkenazi said, stressing that the threat from Hezbollah and Hamas, on Israel's borders, was the most acute.

For the first time, he said, Hamas would have the capability of hitting Tel Aviv from the south, while Hezbollah pounded the coastal city and its industrial environs from the north.

This newfound concentration on defensive systems marks a significant shift in Israel's military doctrine, which in the past has focused on offensive weapons to take the war to its enemies rather than air-defense systems.