U.S. secretary of state delegates duties to deputy, tenure to end March 31

File photo taken on Feb. 2, 2017 shows U.S. Secretary of State Rex Tillerson delivers remarks to employees at the State Department in Washington D.C., the United States. Rex Tillerson said on March 13, 2018 that he was delegating his official duties to Deputy State Secretary John Sullivan, and his tenure would terminate on March 31. (Xinhua/Yin Bogu)