The Secretary-General is authorized to appoint Assistant Secretaries-General and such other officials and employees as are required and to prescribe their responsibilities and duties .. Assistant Secretaries-General shall have responsibility for and supervision of Departments and Services. There shall always be one Assistant Secretary- General designated by the Secretary-Genrral to dcputize for him when he is absent or unable to perform his functions. The Secretary-General shall take whatever steps may be requircd to ,·n,un· thc necessary co-ordination between the Departments of Economic Affairs and of Social Affú,s, and the maintenance of appropriate administrative relationships between those Departments and the Econom:c and Social Council, "n th" one hand, ;i.7d