U.S. President Donald Trump has fired Secretary of State Rex Tillerson and named his spy chief as his top diplomat.

Trump on Tuesday announced the sudden replacement via Twitter, saying that he will be replacing Tillerson with Director of Central Intelligence Mike Pompeo.

Trump tweeted that Pompeo will become the new secretary of state and will do a fantastic job, adding that Gina Haspel will become the new CIA chief. 

After the dismissal, Trump told reporters outside the White House that he and Tillerson "disagreed on things," including how to handle the Iran nuclear deal. 

Tillerson was in favor of remaining in the landmark 2015 agreement between Iran, the U.S. and five other world powers. But Trump frequently criticized the deal and has pledged to drop out unless it is "fixed."

Trump also admitted that he decided to accept an invitation to meet with North Korean leader Kim Jong-un without discussions with Tillerson.

Meanwhile, Undersecretary of State Steve Goldstein was also fired hours after posting a statement in protest of Tillerson's dismissal.