Russia's Foreign Ministry said Thursday that the contract on the supply of S-300 air defense systems to Iran is not covered by the new sanctions imposed on Tehran by the UN Security Council.

"Yesterday's resolution on Iran refers to particular kinds of weapons. I can tell you that all air defense systems with the exception of portables are not liable for the UN conventional arms restrictions," a ministry spokesman, Andrei Nesterenko, was quoted by the Interfax news agency as saying.

Earlier, Interfax reported citing a source that Russia would freeze the contract in light of the new sanctions.

So far, Russian officials have offered conflicting remarks concerning the delivery of S-300 defense systems.

Earlier, Interfax reported citing an arms industry source that Russia would freeze the contract in light of the new sanctions.

However, Konstantin Kosachyov, head of the international relations committee of Russia's State Duma, the lower house of parliament, said no defensive systems, such as S-300 missiles, are on the list of sanctions.

The S-300 air defense system is an advanced mobile system that can shoot down aircraft and cruise missiles from up to 150 km away.

The United States and Israel oppose the sale of the missiles to Iran.

The UN Security Council on Wednesday adopted a resolution to impose a fourth round of sanctions against Iran over its nuclear program.