The United States has expressed concern over Russia's lifting of ban on supplying Iran with arms consisting of sophisticated S-300 air defence missile system.
According to BBC, US Secretary of State John Kerry discussed the matter with the Russian Foreign Minister, Sergey Lavrov in a phone call, said the White house.
Russia lifted the ban as it believes the embargo was no longer necessary after an interim deal was reached on Iran's nuclear programme.
A finalized agreement on Iran's nuclear deal is expected to be reached by June 30 by Tehran and six world powers.
