WASHINGTON — Mark Lewis, the Pentagon’s director of defense research and engineering for modernization, has been temporarily designated to perform the duties of the undersecretary of defense for research and engineering.

Undersecretary Mike Griffin and his deputy, Lisa Porter, announced June 23 that they would step down to pursue a joint job in the private sector.

While the deputy undersecretary would normally be promoted to an acting capacity, the modernization seat had been designated as the next person in line, leaving Lewis as the next man up. Underneath Porter sat Lewis and two other officials: Jim Faist, the director of defense research and engineering for advanced capabilities, and the office of the director of defense research and engineering for research and technology, currently filled in an acting capacity by JihFin Lei.

“Until the official designation of an acting Under Secretary of Defense and an acting Deputy Under Secretary of Defense for Research and Engineering, Dr. Mark Lewis, the current director of defense research and engineering for modernization, is designated as the individual performing the duties of Under Secretary of Defense for Research and Engineering,” Lt. Col. Robert Carver, a department spokesman, said in a statement.

That official designation could come as soon as next week. It is unclear if Lewis is a long-term solution, either as undersecretary or deputy secretary. Politico reported Friday that Secretary of Defense Mark Esper is seeking someone with Silicon Valley experience to take the top job.

Lewis, a well-known figure in defense technology circles, took his current role in November 2019. He was previously director of the IDA Science and Technology Policy Institute, and from 2004 to 2008 served as chief scientist for the U.S. Air Force. As director of defense research and engineering he has oversight over the Pentagon’s key technology modernization priorities, including hypersonic weapons, 5G and artificial intelligence.