Iran boasted on Monday it is manufacturing a home-built air defence missile system which would be better than the Russian S-300, which has been ordered by Tehran but yet to be delivered by Moscow.

"Today, we are building all our air defence weapons by ourselves ... the only thing we wanted to import was the Russian S-300 which so far they have not delivered for some unacceptable reasons," senior airforce commander Heshmatollah Kasiri was quoted as saying by the official IRNA news agency.

"But our air defence experts and scientists found a way and in very near future we will produce an air defence system which has the capabilities of the Russian S-300 or even more."

Kasiri's comments come after Iran in late November threatened to take legal action against Russia if it fails to honour a deal to supply Tehran with the S-300, an advanced air defence missile system.

Russia, Tehran's sole ally among world powers, has so far not delivered the system, in a delay which Iranian officials blame on growing pressure on Moscow from Washington and Iran's arch-foe Israel.

In October, Russia's Interfax news agency reported that Iran had not yet paid for the missile system because Moscow has not given its final approval for the deal, which had set alarm bells ringing in the West.

Under the contract, Russia would sell Iran five batteries of S-300PMU1 missiles for around 800 million dollars (530 million euros), Interfax reported.

The S-300PMU1 -- codenamed the SA-20 Gargoyle by NATO -- is a mobile land-based system designed to shoot down aircraft and cruise missiles.

Western governments fear Iran could use the system to boost defences around its nuclear sites against any Israeli or US air strike.

Neither country has excluded the possibility of a military strike on Tehran's nuclear sites to prevent the Islamic republic acquiring an atomic bomb.

Iran insists its nuclear enrichment programme is for peaceful purposes only.