President Trump denounced his first secretary of state, Rex W. Tillerson, as “dumb as a rock” and “lazy as hell” on Friday after Mr. Tillerson said that the president had regularly pushed him to take actions that were illegal.

Mr. Trump, who fired Mr. Tillerson with a Twitter post in March, lashed back at him the same way after the former secretary gave a talk in Houston and said Mr. Trump was undisciplined, did not like to read and did not respect the limits of his office.

“Mike Pompeo is doing a great job, I am very proud of him,” Mr. Trump wrote on Friday afternoon, referring to the current secretary. “His predecessor, Rex Tillerson, didn’t have the mental capacity needed. He was dumb as a rock and I couldn’t get rid of him fast enough. He was lazy as hell. Now it is a whole new ballgame, great spirit at State!”