Iran hopes that Russia will remain committed to the delivery of the S-300 missile system after Russia agreed to load fuel into its Bushehr reactor, National Security and Foreign Policy Commission deputy head Esmail Kowsari has said.
"After bringing the Bushehr nuclear power plant into operation, we hope that the issue of S-300 missiles will also be discussed and the problem resolved," he said.
Russia had signed a contract to sell Iran at least five S-300 air-defense systems in 2005, but has wavered in delivering the systems.
Iranian Defence Minister Brigadier General Ahmad Vahidi said the deal was not cancelled and that Tehran was following up through negotiations.
The S-300 system is a mobile land-based system designed to detect and shoot down aircraft within 120km (75 miles), according to Fars News Agency.
If delivered, the systems could improve Iranian defences against any air strike on its sites, including nuclear facilities.
Iran has taken delivery of 29 Russian-made Tor-M1 air defence missile systems under a contract in 2005.