Russia and Iran have signed a contract on Moscow’s delivery of the advanced S-300 missile defense system to the Islamic Republic, Sergei Chemezov, chief executive of Russian state-owned defense conglomerate Rostec, said Monday.

“The contract on delivery of S-300 to Iran has not only been signed by the sides but has already entered into force,” Chemezov said at the Dubai Airshow-2015, according to Russian media.

One of the most sophisticated anti-aircraft weapons in the world, the S-300 is capable of tracking multiple planes at once, and some versions have an interception range of up to 200 kilometers.

Israel has long sought to block the sale to Iran of the S-300 system, which analysts say could impede a potential Israeli strike on Tehran’s nuclear facilities. Other officials have expressed concern that the systems could reach Syria and Hezbollah, diluting Israel’s regional air supremacy.

The agreement would allow the delivery of five systems to Iran following a nine-year delay in the $800 million deal. Russia initially agreed to sell the system to Iran in 2007 but then balked, saying at the time it was complying with a United Nations arms embargo on the Islamic Republic.

In April, shortly after the announcement of the Lausanne outline for the nuclear deal between world powers and Iran, Russia announced it was lifting the ban on selling the advanced missile defense system to Iran, over American and Israeli objections.

In August, Iran and Russia announced that the system would be delivered by the end of the year, with Russian Deputy Foreign Minister Mikhail Bogdanov saying at the time that “just technical details” remained to be agreed upon.

Monday’s statements suggesting the final deal has been signed came as Prime Minister Benjamin Netanyahu was set to meet with US President Barack Obama in Washington to discuss US military assistance to Israel for the coming decade. Some of the weapons said to be under discussion reflect the prominence of Iran in US and Israeli military thinking.

Prime Minister Benjamin Netanyahu prepares to board a plane headed to the US, November 8, 2015 (PMO)

Prime Minister Benjamin Netanyahu prepares to board a plane headed to the US, November 8, 2015 (PMO)

The two leaders are expected to discuss commitments that could see Israel get more than the 33 high-tech F-35 jets already ordered, along with precision munitions and a chance to buy V-22 Ospreys and other weapons systems designed to ensure a qualitative Israeli military edge.

The F-35 is the only aircraft able to counter the S-300 surface-to-air missile system. Officials said Israel may also seek to ensure that other US allies in the region do not get the F-35.

The White House has so far rebuffed Arab Gulf states’ requests to buy the planes.

Times of Israel staff contributed to this report.