The Obama administration is expected to announce an additional $680 million in U.S. financial aid aimed at helping Israel purchase additional Iron Dome batteries to intercept rockets.

Defense Minister Ehud Barak will fly to Washington tomorrow, his second trip in less than a month, ahead of the joint Israeli-American announcement of the deal, which was authorized by a U.S. House of Representatives Armed Services subcommittee last month.

Assistance for two other missile defense programs has also been authorized: $165 million for the Magic Wand mid-range anti-missile system, which is under development, and $119 million for the Arrow long-range anti-missile system.

Barak will meet with Defense Secretary Leon Panetta, who announced early last month that the Pentagon was planning to give Israel additional military aid to purchase the batteries.

Israeli security sources said the aid plan was particularly generous, especially considering the economic situation in the United States.

The Obama administration gave Israel $205 million in 2009 for the purchase of four of Israel's six batteries, on top of its $3 billion defense assistance to help launch the missile defense system.

Barak said on Independence Day last month that the U.S. aid means the Israel Defense Forces would be able to acquire a total of 10 Iron Dome batteries, along with thousands of intercepting missiles. The Knesset Foreign Affairs and Defense committee previously said 13 batteries would be needed to protect most of the country from short-range missiles.

While leading defense officials had previously expressed reservations about the Iron Dome system, they now support it enthusiastically - though there are still some experts outside the country's security establishment who doubt the defense system's ability to withstand heavy barrages of rockets.

U.S. President Barack Obama's original budget proposal had no funding request for the missile defense system, but in recent weeks Panetta, citing its success in repelling barrages of rockets launched from the Gaza Strip earlier this year, said the administration would agree to additional funding.

Barak and Panetta are also set to discuss the Iranian nuclear program, less than a week before the start of the second round of nuclear talks between Iran and the five permanent UN Security Council members plus Germany, which will take place in Baghdad on May 23. Israel continues to express doubts over the possibility of forcing Tehran to accept a fair deal that would lift the threat of its developing nuclear weapons.

While the rapid approval of the Iron Dome funding is seen as connected to the system's purely defensive purpose and proven track record in intercepting dozens of Grad Katyusha rockets that Palestinians have launched on Israel from the Gaza Strip over the past year, some see the uptick in U.S. military support as an indirect way to secure Israel's agreement not to take military action against Iran without prior coordination with Washington, especially before the U.S. presidential election in November.

Barak's trip is particularly timely in light of Hezbollah leader Hassan Nasrallah's statement Friday that the time when Lebanese fled their homes because of Israeli bombs, even as Israelis remained in their homes, has come to an end. Nasrallah also said Hezbollah missiles are capable of hitting any target in Israel with great precision.

Col. Ronen Cohen (Res. ), a retired senior Military Intelligence official, said Nasrallah's speech indicated both an interest in retaining a balance of deterrence with Israel and an emphasis on the precision of Hezbollah's missiles.

JTA contributed to this report.