Though it could be years before it is fully operational along Israel's borders, Israeli officials have said the deployment of the system at a few initial locations could begin sometime this year.

'Unshakable'

"As the president has repeatedly said, our commitment to Israel's security is unshakable and our defence relationship is stronger than ever," Vietor said.

"This funding will expand what they can produce and deploy, and how quickly they're able to do it"

Bryan Whitman, Pentagon spokesman

"The United States and our ally Israel share many of the same security challenges, from combating terrorism to confronting the threat posed by Iran's nuclear-weapons programme."

Al Jazeera's Patty Culhane, reporting from Washington, said sources told her that Israel had been working on the "Iron Dome" project for several years.

"A senior department of defence official tells me that recently, US officials saw a test of the project and were very impressed by it, and decided to give the money to help speed up production."

The move comes after ties between Israel and the US were strained by an announcement of more illegal Israeli settlements in East Jerusalem made during a visit to Israel by Joe Biden, the US vice-president.

In January Israel completed tests on its anti-missile system, and the next phase will see it being integrated into the army.

Produced by Israeli state-owned Rafael Advanced Defence Systems Ltd, the "Iron Dome" uses small radar-guided missiles to blow up Katyusha-style rockets with ranges of between five-70 kilometres, as well as mortar bombs, in mid-air.

Bryan Whitman, a Pentagon spokesman, said the funds sought from Congress would be the first direct US investment in the "Iron Dome" system.

"This funding will expand what they can produce and deploy, and how quickly they're able to do it," he said.

According to the US state department, US military aid to Israel in 2009 totalled $2.55bn. This will increase to $3bn in 2012, and will total $3.15bn a year from 2013 to 2018.