Koh was President of the Third United Nations Conference on the Law of the Sea, 1980–1982. Lax and Sebenius present Koh and his efforts in getting the Convention passed, as an example of successful negotiating. 1990 to 1992 he served as Chairman of the Main Committee of the UN Conference on Environment and Development, where he presided over the negotiations on Agenda 21. He has also served as Singapore's ambassador to the United Nations and the United States.