Israel has finalised a deal to purchase 17 more F-35 stealth fighters in addition to 33 of the ultra-high-tech jets already ordered, the defence ministry said Sunday.

Israel has already taken delivery of five of the jets, made by US-based Lockheed Martin and the most expensive in history, beginning in December.

The aim of the purchase is to allow Israel to maintain its military superiority in the turbulent Middle East, particularly regarding its arch-foe Iran and the S-300 anti-aircraft system delivered to it by Russia.

It had previously announced its intent to purchase 17 more planes, bringing the total to 50.

"The F-35 will be a key element in assuring Israel's defence both along our borders as well as far from them," Defence Minister Avigdor Lieberman said.

The cost of the next batch of 17 F-35s will be less than $100 million each, the ministry said, a significant reduction from the initial 33 planes.

Those were purchased at an average of about $110 million each. The cost of the jets has been sharply criticised, including by US President Donald Trump.

Israel's first jets are to be operational this year.

While other countries have ordered the planes, Israel -- which receives more than $3 billion a year in US defence aid -- says it will be the first outside the United States with an operational F-35 squadron.

Among its main features are advanced stealth capabilities to help pilots evade sophisticated missile systems.

The single-pilot jets can carry an array of weapons and travel at a supersonic speed of Mach 1.6, or around 1,200 miles per hour (1,900 kilometres per hour).

The pilot's helmet, at a cost of about $400,000 each, includes its own operating system, with data that appears on the visor and which is also shared elsewhere.

Thermal and night vision as well as 360-degree views are possible with cameras mounted on the plane.

Source: AFP