U.S. President Donald Trump has again cleaned house, this time firing his top diplomat and replacing him with his hawkish spy chief in a move that could have wide-ranging implications for a planned summit between the American and North Korean leaders slated to take place sometime before the end of May.

Trump ousted Secretary of State Rex Tillerson on Tuesday, abruptly ending the pair's rocky relationship via a single tweet announcing his firing. In the tweet, Trump praised Tillerson's service and said he would nominate his CIA director, Mike Pompeo, to be his new secretary of state.

The president's move comes as his administration ramps up preparations for high-stakes and historic talks between Trump and North Korean leader Kim Jong Un, and the change-up — just weeks before that meeting — is likely to put a bumpy road ahead of a State Department that is already grappling with serious challenges, including staffing issues and low morale amid budget cuts.