MOSCOW - Russian President Vladimir Putin said on Thursday Iran's drive to find a solution in talks over its disputed nuclear program had spurred his decision to renew a contract to deliver S-300 missile defense systems to Tehran.Moscow's move to provide the advanced surface-to-air missile system to Tehran, which irked the West and drew protests from Israel, followed an initial agreement with world powers under which Tehran would curb its nuclear program in exchange for lifting of international economic sanctions. "With the progress of the Iranian nuclear track - and that is obviously positive - we do not see any reason to continue to keep the ban (on the delivery of the S-300) unilaterally," Putin told his annual marathon call-in show with Russians.A final deal on Tehran's nuclear program is due by end-June but Moscow has moved quickly to try to secure contracts in Iran before sanctions are lifted and has urged engaging Tehran more in attempts to solve regional crises.Speaking at a Moscow security conference, Russian Foreign Minister Sergei Lavrov said the preliminary deal meant Iran's "vicious" international isolation should come to an end.Russia has been Iran's key ally in the talks with world powers. But Putin also said Russia would still work "as one" with its partners over Iran, and that deliveries of the S-300 would work as a deterrent in the Middle East.Speaking at the security conference, Iranian Defense Minister Hossein Dehghan said the two countries had agreed the sales and were discussing the timing of deliveries.Moscow and Tehran hold similar views on many Middle Eastern conflicts. They criticize the United States for leading air strikes against Islamic State in Syria and Iraq without close cooperation with Damascus.They also denounce strikes led by Saudi Arabia, a US ally, against Iran-allied Houthi fighters in Yemen.Dehghan also played to Russia's own concerns by offering to work with Moscow, Beijing and New Delhi to prevent expansion of NATO and deployment of an anti-missile shield in Europe.Lavrov said plans for the US-led NATO missile shield should now be altered given that the system had originally been meant as protection against rogue states such as Iran. Moscow suspects the system, though defensive, is aimed against itself."If plans for a global anti-missile shield continue to be implemented without any corrections, even given progress in talks over Iran's nuclear program ... the real motives for building the shield in Europe become clear to all," he said.