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Assistant Secretaries-General

Thomas Gass


Thomas Gass was appointed by the Secretary-General as Assistant Secretary-General for Policy Coordination and Inter-Agency Affairs in UN DESA and he took office on 3 September 2013. He brings with him wide-ranging experience in bilateral and multilateral development cooperation. From 2009 to 2013, he served as Head of the Mission of Switzerland to Nepal (Ambassador and Country Director of the Swiss Agency for Development and Cooperation), where he established the Embassy of Switzerland in Nepal, and ensured the delivery of a development cooperation programme of up to 33 million dollars a year. He also chaired the Donors of the Nepal Peace Trust Fund, the main instrument for international support to Nepal’s peace process.

Before his posting to Nepal from 2004 to 2009, Mr. Gass was Head of the Economic and Development Section at the Permanent Mission of Switzerland to the UN in New York, where he represented Switzerland’s interests, in particular in the Economic and Social Council (ECOSOC) and its subsidiary bodies, the General Assembly and the Executive Boards of the major UN Funds and Programmes. During this time, Mr Gass was the Chair of the Donor Group of the UN Global Compact.

In 2006, he was the Vice-President for Western European and Other Group (WEOG) of the Commission on Population and Development, and in 2008 he was the Vice-President (WEOG) of the Executive Board of UNDP/UNFPA. In 2007, he successfully facilitated the landmark TCPR/QCPR Resolution, the periodic review of the General Assembly operational system for development.

Mr. Gass also served as Policy and Programme Officer for the Swiss Agency for Development and Cooperation, as Deputy Resident Representative of the United Nations Development Programme (UNDP) in Guyana, and as Regional Director for Europe with the International Plant Genetic Resources Institute in Rome.

Born in 1963, Thomas Gass holds a PhD in natural sciences from the Swiss Federal Institute of Technology in Zurich and a MSc and engineering diploma in agricultural sciences from the same Institute.


Lenni Montiel

Lenni Montiel was appointed by the Secretary-General as Assistant Secretary-General for Economic Development in the Department of Economic and Social Affairs and took office on 16 January 2015.

With almost thirty years of experience, Mr. Montiel has held strategic positions within the Government of Venezuela and in several international organizations. Throughout his career he has been systematically involved in policy making and analytical work on issues related to economic development.

As Director in the Ministry of Planning and in the Ministry of Family Affairs, he contributed to the design of government policies in Venezuela; he was the lead economist in the team that created the Social Investment Fund of Venezuela in the early 1990s. He also served as Counsellor to the Executive Director for Venezuela and Panama at the Board of Directors of the Inter-American Development Bank.

At the UN, Mr. Montiel has built a career as economic and policy adviser to both senior government officials at national and local levels and he has worked in several countries and in different capacities. He was UN Resident Coordinator in Turkmenistan and provided long term policy support to national development efforts in Vietnam, Ukraine, Belarus, Bolivia, Chile, Colombia, Ecuador, Costa Rica, Kazakhstan, Mauritius, Peru, Romania and the Territory of Kosovo.

At the Bureau for Development Policy in UNDP in New York, Mr. Montiel was a Senior Policy Adviser leading large teams of policy advisers working around the globe through the management of several professional communities of practice. He was the architecture and Network Facilitator of LOGOV- “Innovations in Local Governance Electronic Initiative”, that was acknowledged as a “Good Practice” in the 1998 UNCHS-HABITAT Best Practice International Award.

Since 2012, Mr. Montiel worked as Director for Economic, Social and Development Affairs in the Executive Office of the Secretary-General, leading the analytical work in the area of economic and development affairs.

Mr. Montiel was trained as an economist in the former Soviet Union, where he received his first university degree and a MSc in Economics – National Planning from the Belorussian National Institute of National Planning. He strengthened his academic and research capacities by obtaining a PhD in Public Policy from Birmingham University and a MA on Legislative Studies from the University of Hull in the United Kingdom.


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