President Trump has been telling advisers that he plans to soon remove Department of Homeland Security Secretary Kirstjen Nielsen, the Washington Post reported Monday. She could be ousted in the next few weeks and as soon as this week.

Trump’s frustrations with Nielsen have come from his impatience over immigration issues. Trump has reportedly berated Nielsen repeatedly in Cabinet meetings and blamed her for the continued arrival of Mexican and Central American migrants at the border, and Nielsen has expressed frustration to her aides that the president does not understand the complications of immigration law that limit her ability to take drastic action or the realities of border security that make some measures impractical or unreasonable.

According to the Post, Trump told aides that he wants Nielsen out as soon as possible, and he canceled a planned trip with her this week to visit soldiers at the border.

If Trump goes through with the firing, he will likely look for someone who will be more eager to implement his immigration-policy ideas. However, chief of staff John F. Kelly is reportedly fighting to have Trump keep Nielsen and is advocating for her across the administration. White House officials told the Post that Kelly’s own future may not be so certain either.

If Nielsen were to leave without an immediate replacement on deck, the job of managing the agency day to day will fall to Claire Grady, the undersecretary for management, as the job of deputy secretary at DHS has been vacant since April. Trump may name another Senate-confirmed official to run the agency.