The agreement to supply Russian S-300 air defense systems to Iran is in the execution stage, Iranian Foreign Ministry spokesman Hussein Jaber Ansari said Monday.

On April 11, the Iranian Foreign Ministry announced that Russia had made the first contracted delivery of the S-300 systems as scheduled.

"The agreement on S-300 is being implemented. We hope that its implementation will be conducted in a natural way," Ansari said.

Iran unveiled its first S-300 systems during an annual Army Day parade in mid-April.

The $900-million Moscow-Tehran contract to deliver five Russian S-300 systems to Iran was signed in 2007. It was suspended after the adoption of UN Security Council sanctions on Iran in mid-2010, Sputnik reports.

In April 2015, Russia resumed the talks on S-300 deliveries following a framework agreement on the landmark deal ensuring the peaceful nature of Tehran’s nuclear program. The first delivery under the contract took place earlier in April.

Russia and Iran are expected to fulfill the S-300 contracts in 2016, according to the Iranian defense officials.

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