Ambassador de Klerk is the Netherlands ambassador to Jordan. He is also the sherpa for the Nuclear Security Summit, which will be held in the Netherlands in 2014. Previously, he was the deputy permanent representative of the Netherlands at the United Nations in New York; ambassador for human rights at the Netherlands Ministry of Foreign Affairs; and the director of the office of external relations and policy coordination at the International Atomic Energy Agency in Vienna. He also worked in different positions at the Netherlands Ministry of Foreign Affairs: as desk officer in the disarmament & peace affairs section; deputy resident representative to the IAEA and deputy permanent representative to the UN in Vienna; the head of the verification section, and later arms control bureau in the international security affairs department. He taught physics and society courses as an assistant professor at the University of Amsterdam.