(CNN) President Donald Trump said Sunday that he anticipates shifting several positions in his administration, hinting that the departures could include Homeland Security Secretary Kirstjen Nielsen and White House chief of staff John Kelly.

"I have three or four or five positions that I'm thinking about," Trump told Fox News' Chris Wallace during an interview that aired on "Fox News Sunday." "Of that, maybe it's going to end up being two. Maybe. But I want to -- I need flexibility."

Trump has been mulling an administration shakeup in recent weeks, with Nielsen anticipated as possibly the next to go , multiple officials with knowledge of the matter have told CNN. The officials describe Trump as dissatisfied over Nielsen's handling of his key issues of immigration and border security. Trump has also floated possible replacements for Kelly, including Vice President Mike Pence's chief of staff, Nick Ayers.

In the interview, Trump praised Nielsen as intelligent, but stressed that she was not as "tough" as he wanted her to be.

"I like her a lot. I respect her a lot. She's very smart," Trump said of Nielsen. "I want her to get much tougher, and we'll see what happens there. But I want to be extremely tough."

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