Kevin Hassett told CNBC on Monday his impending departure as White House economic advisor is not related to President Donald Trump's tariff threats on China and Mexico.

Hassett has been chairman of the White House Council of Economic Advisers for about two years.

"This is something that's been in the works for a little while," Hassett said in "Squawk Box" interview. "If you look at the history of the CEA, it's very normal for the chair to move on after two years."

He said he is leaving at the end of this month.

Trump tweeted on Sunday that Hassett will "shortly" leave his post, saying he's "done such a great job for me and the administration" and "his very talented replacement will be named as soon as I get back to the U.S."

Trump began a five-day trip to Britain, France and Ireland on Monday.

Kevin Hassett, who has done such a great job for me and the Administration, will be leaving shortly. His very talented replacement will be named as soon as I get back to the U.S. I want to thank Kevin for all he has done - he is a true friend

Hassett, who said he's unsure of his next position, said the departure is partly out of "respect for the institution" and to spend time with his family.

"The longer you stay in the White House, the closer you get with everybody in the West Wing," he said. "It's normal, circle of life kind of stuff."