The head of Customs and Border Protection will leave his post at the end of the month.
The agency said Commissioner Alan Bersin told President Barack Obama on Thursday that he intended to leave office Dec. 30, the day before his appointment to the job expires.
David Aguilar, former chief of the Border Patrol and the number two official at CBP, has been named the acting commissioner.
Obama nominated Bersin to head the agency in September 2009 and appointed him commissioner in March 2010, after the Senate didn't act on the nomination. Bersin was one of 15 officials to receive a recess appointment that year.
In a statement, Bersin said he was "proud of the significant and meaningful achievements we have made on our borders and at our nation's ports of entry over nearly two years."
Bersin served as Obama's border czar, a post the administration created to focus on issues related to illegal immigration and relations with Mexico in its war against drug cartels, before being elevated to head of CBP. He also previously helped coordinate law enforcement efforts at the Mexican border during the Clinton administration while he was working at the Justice Department.