UNITED NATIONS (Reuters) - U.S. unilateral sanctions on Iran undermine the Iran nuclear deal, Russian Foreign Minister Sergei Lavrov said on Thursday.  Using unilateral sanctions ... is illegitimate and undermines the collective nature of international efforts. Everyone is witnessing with alarm today the newer and newer restrictions by the U.S. against Iran,  Lavrov told the U.N. General Assembly annual gathering of world leaders.  They threaten the implementation of the Joint Comprehensive Plan of Action,  he added, referring to the 2015 international accord between Iran and six world powers. 