Donald Trump announced Tuesday that Secretary of State Rex Tillerson was being replaced by CIA director Mike Pompeo.

Trump made the announcement via Twitter, also revealing that Gina Haspel, deputy director of the CIA, would replace Pompeo at the agency. She will be the first woman to hold the position.

The Washington Post reports that Trump asked Tillerson to step aside last Friday and the former Exxon Mobil executive cut short his trip to Africa to return to Washington Monday.

In a statement to the Post, Trump offered his thanks to Tillerson:

“I want to thank Rex Tillerson for his service. A great deal has been accomplished over the last fourteen months, and I wish him and his family well.”

Tillerson’s firing comes as the U.S. begins preparations for a historic meeting between Trump and Kim Jong Un, scheduled to take place by the end of May.