Then-Assistant Secretary of State for Near East Affairs Anne W. Patterson stands at attention during the Sunset Parade at the Marine Corps War Memorial in Arlington, Va., on July 29, 2014. (Lance Cpl. Alejandro Sierras/Marine Corps)

Defense Secretary Jim Mattis has asked recently retired diplomat Anne W. Patterson to become his undersecretary of defense for policy, the third-ranking policy job at the department.

Patterson and Mattis, the former chief of U.S. Central Command, worked together frequently when she served as ambassador to Pakistan and to Egypt. She retired in January after more than three years as assistant secretary for Near East affairs, the State Department’s top official on the Middle East, at the highest rank of career diplomat.

The appointment, which requires Senate confirmation, is still awaiting White House approval, according to people familiar with the discussions. It was first reported by Politico.

Mattis, who reportedly insisted he be able to choose his own team when he accepted President Trump’s offer to head the department, has skirmished repeatedly with the White House over appointments. His initial choice for deputy secretary, Michèle Flournoy, withdrew from consideration following meetings with White House officials. Flournoy served as the department’s policy undersecretary during the Obama administration.

The current Defense Department deputy, Robert Work, is a holdover from Barack Obama’s presidency who has agreed to remain in office for several months until his successor is in place. The deputy slot also remains vacant at the State Department, where Secretary Rex Tillerson’s reported choice, Elliott Abrams, was reportedly rejected by the White House.

Hundreds of senior policy positions remain vacant and without nominees across the executive branch six weeks into the Trump administration. Although Patterson retired before the inauguration, top diplomats in most of the State Department’s regional and policy offices were effectively fired once Trump took office. Next week, the last remaining regional assistant secretaries — for Africa and the Far East — are stepping down.

In his budget outline this week, Trump proposed sharp cuts at the State Department to help fund a $54 billion increase in defense spending.

Patterson, who has never worked at the Defense Department, also served as top U.S. diplomat in Colombia and El Salvador.

In Egypt, she was ambassador from 2011 to 2013, a period marked by upheaval resulting in the military overthrow of elected president Mohamed Morsi and estrangement between the Obama administration and the Egyptian army general who took power, Abdel Fatah al-Sissi.

Trump has largely dismissed Obama-era criticisms of Sissi’s repression of human and civil rights and praised Egypt as an effective counterterrorism ally.