Original sentence: In 2000 he joined the UN Secretariat in New York  From 2000-2002 he was a policy analyst in the Office for the Coordination of Humanitarian Affairs and then transferred to the United Nations Department of Political Affairs, becoming in 2004 head of the Policy Planning Unit in that department
Edited sentence: In 2000 he joined the UN Secretariat in New York, first with the Office for the Coordination of Humanitarian Affairs and then with the United Nations Department of Political Affairs, becoming in 2004 head of the Policy Planning Unit in that department