Sen. Thom Tillis (R-NC) said Sunday that deputy White House chief of staff Stephen Miller is a “big problem” for the Trump administration as it seeks to deliver on border security.

Tillis said he is glad President Donald Trump “moved on” from Kristi Noem’s leadership at the Department of Homeland Security, expressing hope that his “friend” Sen. Markwayne Mullin (R-OK) can “fix what’s broken” at DHS.