seoul south korea president moon jae-in u.s. president donald trump agree exert strong pressure sanction north korea follow nuclear missile test south korea presidential office say follow telephone call two leaders sunday two leaders agree strengthen cooperation exert strong practical sanction north korea realize provocative action lead diplomatic isolation economic pressure blue house spokesman park soo-hyun say televise brief blue house say moon trump strongly condemn late missile launch north korea agree two nations would work international community implement late un security council resolution 2375 park say south korea say moon trump agree need strong north korea sanction