Russian S-400 System (image: AFP)

Russia has rejected Iran's request of buying the S-400 anti-aircraft, missile defense systems, a senior Russian official told Bloomberg on Friday.

"The request was rebuffed by President Vladimir Putin, who was concerned that the sale would stoke more tension in the Middle East," the officials said on the condition of anonymity.

“Any real or imaginary strengthening of Iran can lead to escalation — if Russia really refused Iran such a request, it would mean that Russia wants to keep working on relations with Saudi Arabia, Israel and keep a chance for negotiations with Trump,” Ruslan Pukhov, head of the Center of Analysis of Strategies and Technologies in Moscow, said.

“If Russia decides to provide Iran with S-400, it will be a direct challenge to Saudi Arabia and Israel, so it will be against Russia’s own national interests.”

In 2010, Iran's refusal to halt its Uranium enrichment program led the UN to impose sanctions against the sale of heavy weapons to the country, leading to the cancellation of delivery of the Russian S-300 system. Along with the sanctions, the decision of then President Dmitry Medvedev to ban arms sales to Iran resulted in the latter incurring losses of $13 billion. The move forced Iran to look at China for its military equipment needs.

After the US imposed sanctions against Russia and Iran, Russia began supporting Joint Comprehensive Plan of Action (JCPOA) or the "Iran Nuclear Deal." Following the JCPOA agreement, President Vladimir Putin lifted the ban, and the country agreed to deliver the S-300 missile defense system to Iran. The delivery of the systems was completed in November 2016. Iran then signed a $10 billion deal for helicopters, warplanes and artillery systems.

Meanwhile, US has also officially threatened Turkey, a NATO member state, of imposing CAATSA (Countering American Adversaries Through Sanctions Act) sanctions against it, if it went ahead with the S-400 purchase. The US also warned India that its S-400 buy would have "serious implications" on US-India defense ties.