President Vladimir Putin on Monday sanctioned the delivery of a highly capable Russian air defense missile system to Iran, a game-changer move that would significantly bolster the Islamic republic’s military capability and fuel Israel’s concerns.

U.S. Secretary of State John Kerry objected to Moscow’s decision in a phone call to Russian Foreign Minister Sergey Lavrov, and the White House indicated Russia’s action could endanger plans to ultimately lift sanctions on Iran as part of a proposed nuclear deal.

White House press secretary Josh Earnest said unity and coordination with nations like Russia is critical to the success of the negotiations. Washington has said Moscow played a constructive role in the Iranian nuclear talks, despite sharp differences between Russia and the West over Ukraine.

Putin’s move was quickly welcomed by Tehran, while it worried Israel, which saw it as a sign that Iran already had begun to cash in on the emerging nuclear deal with world powers that is expected to be finalized by the end of June.

Putin’s spokesman, Dmitry Peskov, said the missile system could be shipped to Iran at any moment.

Russia signed the $800 million contract to sell Iran the S-300 missile system in 2007, but suspended delivery three years later because of strong objections from the United States and Israel.

The preliminary agreement on settling the Iranian nuclear standoff struck earlier this month made the 2010 ban unnecessary, Lavrov said in a televised statement.

The framework agreement reached by Iran and six world powers is intended to significantly restrict Iran’s ability to produce nuclear weapons while giving it relief from international sanctions. The agreement is supposed to be finalized by June 30, and there is no firm agreement yet on how or when to lift the international sanctions on Iran.

The S-300 missile system, which has a range of up to 125 miles and the capability to track down and strike multiple targets simultaneously, is one of the most potent air defense weapons in the world.

“The S-300 is exclusively a defensive weapon, which can’t serve offensive purposes and will not jeopardize the security of any country, including, of course, Israel,” Lavrov said.

Deployed in big numbers, the system could provide a strong deterrent against any air attack. If Israel decides to attack Iran’s nuclear facilities, the S-300s would further complicate the already daunting task.

Israeli Cabinet minister Yuval Steinitz said the framework nuclear agreement helped legitimize Iran and cleared the way for Monday’s announcement by Russia.

“This is a direct result of the legitimacy that Iran obtained from the emerging nuclear deal,” Steinitz said. “Instead of demanding Iran stop its terror activities that it spreads in the Middle East and the entire world, it is being allowed to arm itself with advanced weapons that will only increase its aggression.”

Israel has harshly criticized the U.S.-led nuclear deal, saying it would give Iran relief from sanctions while leaving its nuclear program largely intact. Israel believes Iran still intends to develop a nuclear weapon.

Israeli Prime Minister Benjamin Netanyahu didn’t specifically mention the Russian move Monday, but poured scorn on the proposed nuclear agreement, saying that “Iran draws encouragement from the concessions that it is receiving from the major powers.”

“It is a deal that leaves Iran in possession of the capability to arm itself with nuclear weapons, that fills its coffers with a lot of money and that not only enables it to continue its terrorism and aggression in the Middle East and around the world but does not even demand that it stop doing so,” he said.

Moscow’s plans to sell the S-300s to Iran long have been an irritant in Russia-Israeli relations. In recent years, Israel has refrained from providing sophisticated weapons to Georgia and Ukraine as part of an “understanding” with Russia that it not sell the s-300s to Iran — a position that now may change.

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Russian officials previously said that the specific model of the S-300 that Russia was to deliver under the 2007 contract is no longer produced, and offered Iran a modified version of it called S-300VM, or Antey-2500.

But instead of manufacturing new missile systems for Iran, Russia may provide some S-300s from its own military arsenals. In that case, the delivery may happen quickly.

In Tehran, Iranian Defense Minister Gen. Hossein Dehghan welcomed Russia’s decision to lift the ban. “The decision is the translation of political determination of leaders of both countries for improving and promoting cooperation levels in all fields,” Gen. Dehghan was quoted by the official IRNA news agency as saying.

Back in 2010, Russia linked its decision to freeze the missiles’ delivery to the sanctions the United Nations Security Council imposed on Iran over its nuclear program, but Lavrov argued Monday that the Russian move was voluntary and not directly required by the U.N. resolutions.

“It was done in the spirit of good will in order to encourage progress in talks,” Lavrov said. “We are convinced that at this stage there is no longer need for such an embargo, specifically for a separate, voluntary Russian embargo.”

Iran responded to the Russian ban by filing a lawsuit with a court in Geneva seeking $4 billion in damages for breach of contract, but the court has not issued a ruling.

Lavrov said that Russia had to take into account “commercial and reputational” issues linked to freezing the contract.

“Because of the suspension of the contract, Russia has failed to receive significant funds,” he said. “We see no need to continue doing that.”

He added that Iran badly needs modern air defense systems because of a tense situation in the region, specifically in Yemen.

Observers said the go-ahead on the S-300 deliveries could reflect Moscow’s maneuvering to secure a niche at the lucrative Iranian market before other powers move in.

Vladimir Sazhin, an expert on Iran with the Moscow-based Institute for Eastern Studies, said the move came “at the turning point, when the Iranian market is becoming a strong attraction.”

“Preparation is already going on for the day when the sanctions are lifted and everyone will rush to Iran,” he was quoted by Interfax as saying.

Lifting the ban could also mark an attempt by the Kremlin to raise the heat on Washington and its allies and make them more willing to listen to Russian arguments in the Ukraine crisis.