Secretary-General of the United Nations the appointee's national origin and to gender equality, although no woman has yet served as Secretary-General. The length of the term is discretionary, but all Secretaries-General since 1971 have been appointed to five-year terms. Every Secretary-General since 1961 has been re-selected for a second term, with the exception of Boutros Boutros-Ghali, who was vetoed by the United States in the 1996 selection. There is a term limit of two full terms, established when China cast a record 16 vetoes against Kurt Waldheim's third term in the 1981 selection. No Secretary-General since 1981 has attempted to secure a third term. The
Under-Secretary-General of the United Nations diplomatic immunity under the UN Charter. The majority of USGs are appointed by the UN General Assembly on the recommendation of the Secretary-General for a fixed term of four years. Others (normally special envoys, Secretariat-appointees and non-programme management positions) are appointed directly by the UN Secretary-General on his own authority. However, all USGs report to the UN General Assembly through the UN Secretary-General. The only exception to this is the Under-Secretary-General for Internal Oversight Services who reports directly to the General Assembly. The distinction in method of appointment is important as USGs appointed by the General Assembly have a mandate