White House Deputy Chief of Staff Kirstjen Nielsen will be nominated by President Trump to be the new Secretary of Homeland Security. 

If confirmed, Nielsen would replace White House Chief of Staff John Kelly. Kelly served as Trump’s DHS chief for just over six months before replacing Reince Priebus as chief of staff July 31. Elaine Duke has been filling in as acting secretary in the meantime.

Nielsen would be the first former DHS staffer to lead the department, which was created by former President George W. Bush in 2003.

Nielsen had served as Kelly’s deputy at DHS and followed him to the White House when he replaced Priebus. Her departure leaves Kelly looking to fill another crucial administrative vacancy.

Neilsen is an expert in homeland and national security policy. She previously worked as a special assistant to George W. Bush and for the Transportation Security Administration. 

In a New York Times profile last month, Nielsen was described as “brusque” and “no-nonsense.” The piece claimed that some in the administration had “chafed under a woman asserting power — and made her a target for the anger that they can not express at [Kelly].”

It was not immediately clear when Nielsen’s nomination would be announced.

Fox News’ John Roberts and the Associated Press contributed to this report.