Secretary of Defense Jim Mattis wants to tap the former U.S. ambassador to Egypt, Anne Patterson, as his undersecretary of defense for policy, but the Pentagon chief is running into resistance from White House officials, according to multiple sources familiar with the situation.

If nominated and confirmed, Patterson would hold the fourth most powerful position at the Pentagon – and would effectively be the top civilian in the Defense Department, since both Mattis and his deputy, Robert Work, were military officers.

As ambassador to Egypt between 2011 and 2013, Patterson worked closely with former Egyptian President Mohammed Morsi and his Islamist government. She came under fire for cultivating too close a relationship with the regime and for discouraging protests against it—and White House officials are voicing concerns about those decisions now.