John A. Heffern is an American diplomat. Heffern served as the United States Ambassador to Armenia from 2011 to 2014. After being nominated on May 18, 2011 by United States President Barack Obama, Heffern was confirmed by the U.S. Senate on September 26, 2011 and sworn in as ambassador on October 6, 2011. He was replaced by Ambassador Richard M. Mills Jr. in early 2015.

Richard Merrill Mills Jr. is an American diplomat who serves as the United States deputy ambassador to the United Nations. He served as the U.S. Chargé d'Affaires and Acting Permanent Representative to the United Nations between January 20, 2021, and February 24, 2021, when Linda Thomas-Greenfield became ambassador. In July 2022, he was announced as the nominee to serve as the United States ambassador to Nigeria.