UN Secretary-General Antonio Guterres lays a wreath to honor UN staff members fallen in the line of duty, at the UN headquarters in New York, Jan. 3, 2017. Antonio Guterres started on Tuesday his work as the new chief of the world organization. He told UN staff members that the UN needs their collective engagement to make changes to achieve the goals of the organization on peace, security and development. (Xinhua/Li Muzi)