The delivery of an upgraded interceptor currently being installed on Israel's Arrow anti-missile batteries will ramp up its ability to cope with threats from Syria and Iran, defence experts say.

"The upgraded Block 4 system will significantly improve the accuracy of the existing Arrow 2 missile defence system," an official at the Israeli defence ministry told AFP.

He was referring to the latest upgrade of Israel's cutting-edge missile interception programme which began as a joint project with the United States in the 1980s.

"We find ourselves in a technological race whereby our defence systems must keep up with offensive threats," the source said.

The Block 4 upgrade incorporates a new generation of radar and other technologies which will be synchronised with US systems that are already in use in the region.

"This synchronisation of systems will allow for better tracking of an enemy missile or salvo of missiles fired at our territory," an Israeli defence official said, speaking on condition of anonymity.

One of the most advanced anti-ballistic missile systems in the world, the Arrow 2 was developed in the mid-1990s to counter regional missile threats coming from Syria, Saudi Arabia and Iraq.

But with rising tensions over Iran's nuclear programme and nearly 18 months of bloody unrest in Syria, the focus has shifted.

"With Block 4, the Arrow 2 responds more effectively to the threat posed by (Syrian) Scud D missiles and (Iranian) Shahab missiles," the official told AFP.

Last month, Iran test-fired its medium-range Shahab-3 missile which can travel up to 2,000 kilometres (1,200 miles), making it theoretically capable of hitting Israel, which is just 1,000 kilometres away.

Experts say Syria has a stockpile of Scud and SS-21 ballistic missiles which can be used to deliver chemical weapons.

In February, Israel and the United States carried out a final test of the system before delivery of Block 4, which the defence ministry said would be a "major milestone" in the development of the Arrow.

Work on the Arrow system began in 1988 during the now-defunct Star Wars programme and was stepped up after Israel was hit by 39 Iraqi Scud missiles during the 1991 Gulf War over Kuwait.

Development of the system is half-funded by the United States.

Since the system became operational just over a decade ago, it has undergone numerous improvements, to the point where its interception rate currently stands at between 80 and 90 percent.

Although the upgrade was delivered as tensions rise over Syria and Iran, experts say the timing is fortuitous.

"The Arrow programme began well before the emergence of the Iranian threat and has since been adapted accordingly," said reserve Brigadier General Uzi Rubin, who was responsible for Israel's anti-missile defence system between 1991-1999.

From his perspective, Block 4 is "an evolution and not a revolution."

"Today, there is a threat which is at least as important as that posed by Iranian missiles -- and that is the chemical weapons held by the Syrian regime," he told AFP.

With spiralling violence across Syria, Israel has raised concerns about the fate of Damascus's stockpile of advanced weaponry, which includes surface-to-surface missiles and chemical weapons.

Last month, Defence Minister Ehud Barak warned that Israel would not tolerate the transfer of any such arms to Lebanon's Hezbollah, suggesting it could spark an Israeli military response.