condemned by Israel, the most vehement opponent of the talks between Iran and the five permanent members of the UN Security Council plus Germany.
Iran insists its nuclear programme is for peaceful energy development rather than military purposes.
Russia said progress in nuclear talks, which could see Iran agree to curbs and rigid inspections for at least a decade in exchange for sanctions relief, meant there was no longer a need for it to prohibit export of the S-300 surface-to-air missiles.
Iran, which hailed Russia’s move as a step toward “lasting security” in the region, currently lacks advanced air defences that could knock out modern fighter aircraft in the US or Israeli air forces.
The S-300 is designed to detect and destroy ballistic missiles, cruise missiles and aircraft at low altitude.
Although the S-300 would provide a major improvement for Iran’s air defences, it remains unclear if the missile would be a match for America’s stealthy F-22 fighters and bombers, experts say.
Meanwhile, Iran’s military is purely for defence and should not be seen as a threat in the Middle East, President Hassan Rouhani said on Saturday amid rising tension with Saudi Arabia.
With a Saudi-led air campaign against Huthi rebels in Yemen putting Tehran, the region’s dominant power, at odds with its Sunni rival Riyadh, Russia this week moved to supply missiles to Iran.
Saudi Arabia accuses Iran of arming the Huthis, Yemen’s Zaidi Shiite minority which has long complained of marginalisation and has fought several conflicts with central authorities.
The arms allegation is denied by Iran, which has presented a four-point peace plan for Yemen to UN chief Ban Ki-moon, demanding international action to end the “senseless” Saudi-led air strikes.
Rouhani, whose comments came after renewed intense bombing hit Yemen and al-Qaeda seized more ground in the chaos, said the Islamic republic’s military policies are wrongly perceived.
“Our strategy has always been that of a deterrent... not a doctrine of war,” he said in a speech at an annual Army Day ceremony in the capital where a new Iranian-made Bavar-373 missile was paraded.
The presence of Iranian navy ships “in the Persian Gulf and the Gulf of Aden is intended to ensure the security of neighbouring countries and maritime traffic,” he said.
“The armed forces bring peace to the nation and other peoples of the region,” he added.
Russian President Vladimir Putin earlier this week removed the ban on supplying Iran with a more sophisticated S-300 air defence missile system, paving the way to conclude a long-delayed contract.