Chowdhury was appointed in March 2002 by the
Secretary-General of the United Nations as
Under-Secretary-General and
High Representative for the Least Developed Countries, Landlocked Developing Countries and Small Island Developing States. In December 2003, Chowdhury was designated as the Secretary-General of the International Meeting for the ten-year review of the Barbados Programme of Action for the Sustainable Development of the Small Island Developing States held in
Mauritius from 10 to 14 January 2005. Chowdhury was also designated the Secretary-General of the International Ministerial Conference of Landlocked and Transit Developing Countries and the Donor Community on Transit Transport Cooperation held in
Almaty,
Kazakhstan on 28–29 August 2003. Prior to his appointment, Chowdhury completed his assignment (1996–2001) as
Permanent Representative of Bangladesh to the United Nations in New York City. He also served as Bangladesh's Ambassador to
Chile,
Nicaragua,
Peru and
Venezuela, as well as Bangladesh's High Commissioner to the
Bahamas and
Guyana. During his tenure as Permanent Representative, Chowdhury served as
President of the
Security Council, President of the United Nations Children's Fund (
UNICEF) Executive Board and Vice-President of the
Economic and Social Council of the UN in 1997 and 1998. He had served for more than 10 years as the Coordinator for the Least Developed Countries in New York City. In May 2001, he led the negotiations on behalf of the least developed countries at the Third United Nations Conference on Least Developed Countries, which adopted the comprehensive Brussels Programme of Action for the present decade. Chowdhury also chaired the Fifth (Administrative and Budgetary) Committee of the
United Nations General Assembly in 1997–1998. From 1990 to 1993, Chowdhury was the UNICEF Director for Japan, Australia and
New Zealand. At the first annual Peace Education Conference, held virtually in September 2021, Chowdhury was the inaugural keynote speaker, as Founder of the Global Movement for the Culture of Peace. Also featured was Dr. Stéphane Monney Mouandjo, Director-General of CAFRAD, a UNPAN member, along with other dignitaries. ==Education==