Jeffrey joined the US Foreign Service in 1977. After a training assignment in Tunis, Tunisia he was posted to Sofia, Bulgaria, where he served as the on-site U.S. representative during a hijacking of a Turkish Air Flight with five U.S. businessmen taken as hostages, in May 1981. Jeffrey then served on assignments in Adana and Ankara, Turkey as a political-military officer, from 1983 to 1987. Jeffrey served in Munich, Germany, during the collapse of the Soviet Union and the reunification of Germany from 1989 to 1991, including as acting principal officer during the first Gulf War, and liaison to Radio Free Europe. He then was selected as the State Department's coordinator for the Conference for Security and Cooperation in Europe. Jeffrey later served as the Deputy Presidential Special Advisor for Bosnia Implementation, working to put into place the Dayton Accords.
In 1996 Jeffrey was selected as Deputy Chief of Mission to the American Embassy Kuwait, and served during Operation Desert Fox and the evacuation of Embassy Kuwait. In 1999 he returned to Turkey, as Deputy Chief of Mission. After serving as Ambassador to Albania from 2002 to 2004, he was selected by Secretary of StateColin Powell and Ambassador John Negroponte to bridge the transition from the Coalition Provisional Authority to the new U.S. Embassy in Baghdad, and subsequently served as Deputy Chief of Mission from 2004 to 2005. He served as Chargé d'Affaires in Baghdad before returning to Washington to serve as Secretary of State Condoleezza Rice’s Special Advisor for Iraq from 2006 to 2007. Jeffrey then served as Principal Deputy Assistant Secretary for Near Eastern Affairs, covering broader Middle East policy matters, including co-chairing the Interagency Iran Policy Group. President George W. Bush nominated Jeffrey as Ambassador to Turkey in 2008, where he served in his fourth and final assignment to Turkey until 2010. President Barack Obama nominated him to serve as Ambassador to Iraq in 2010. Jeffrey oversaw its expansion into the largest Embassy in the world with almost 16,000 employees and an annual budget of over $6 billion, and worked with the U.S. military to ensure a successful transition to a civilian lead. According to Voice of America, after this successful transition, Iraq is now increasingly coming under the control of Iran. Along with being the U.S. ambassador for Syrian engagement during the Syrian Civil War, he also assumed the role of Special Presidential Envoy for the Global Coalition to Counter the Islamic State of Iraq and the Levant on 4 January 2019.
Jeffrey has received the Secretary of State's Distinguished Service Award on two occasions, in 2010 and 2012, as well as the Secretary of State's Career Service Award in 2012, and the Distinguished Honor Award in 2005. Secretary Leon Panetta presented him with the Department of Defense Medal for Distinguished Civilian Service in 2011, and CIA Director David Petraeus awarded Jeffrey the Director's Medal in 2012. He received Boston University's School of Management Award for Distinguished Service in 2006, and the American Bar Association's Award for Promoting Rule of Law Worldwide in 2004. His military awards include the Bronze Star.
Personal life
Jeffrey is married with two children and is a resident of Virginia.