The source said no payments have been made because Russia's government has not given its final approval for the sale of S-300 missiles to Iran, a deal that has raised alarm in the West.
"Despite the fact that the contract was signed several years ago, Russia has still not confirmed its entry into force. Thus Iran has not made any payments under this contract," the unnamed source told Interfax.
"The contract to deliver S-300 systems to Iran was frozen indefinitely due to an array of circumstances practically right after it was signed," he said, adding that a political decision would determine the deal's future.
"Much depends on an array of political circumstances, since this contract has ceased to be simply a commercial deal," he said.
Under the contract, Russia would sell Iran five batteries of S-300PMU1 missiles for a total sum of around 800 million dollars (530 million euros), Interfax reported, citing "unofficial information."
The S-300PMU1, called the SA-20 Gargoyle by NATO, is a mobile land-based system designed to take down aircraft and cruise missiles.
Western governments fear that Iran could use the systems to enhance defences around its nuclear facilities against a possible US or Israeli air strike aimed at preventing Tehran from building an atomic bomb.
Moscow has never officially confirmed that it signed the contract with Iran but has repeatedly insisted it has the right to sell "defensive" weapons systems to the Islamic Republic.
