Sievers retired in December 2019 as a career member of the US Senior Foreign Service with the rank of minister-counselor. His last position was as US ambassador to Oman from January 2016 to November 2019. Prior to his appointment he was a diplomatic fellow at the Washington Institute for Near East Policy from September 2014 to July 2015. Sievers is the first person to be appointed to this position, which is a collaborative program with the US Department of State.