WASHINGTON (Reuters) – U.S. President Donald Trump said on Saturday he had a good relationship with Secretary of State Rex Tillerson but that Tillerson could be tougher.

Trump, who made the comment to reporters at the White House, did not elaborate.

NBC reported this week that in a session with Trump’s national security team and Cabinet officials at the Pentagon, Tillerson had openly criticized the president and referred to him as a “moron.”

Tillerson on Wednesday said he had never considered resigning and was committed to Trump’s agenda, but failed to address whether he had referred to the president as a “moron,” as NBC reported.