MOSCOW - Russian President Vladimir Putin said on Thursday Iran's willingness and flexibility in trying to find a solution with the West over its nuclear program had spurred his decision to renew a contract to deliver an S-300 missile defense system to Tehran. But the president, in his annual televised call-in show, said Russia would still work 'as one' with its partners in the United Nations over Iran and that deliveries of the S-300 would work as a deterrent in the Middle East. 'And now 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,' he said.