President Donald Trump on Thursday tore into former Secretary of State Rex Tillerson over comments he reportedly made to members of the House Foreign Affairs Committee this week.

Tillerson, whom Trump fired by tweet in March 2018, told lawmakers that Russian President Vladimir Putin was better prepared than Trump for a key meeting in Germany in 2017, The Washington Post reported, citing unnamed committee aides.

“We spent a lot of time in the conversation talking about how Putin seized every opportunity to push what he wanted,” a committee aide told the Post. “There was a discrepancy in preparation, and it created an unequal footing.”

Trump fired back on Twitter, repeating his characterization of Tillerson as “dumb as a rock” and accusing him of lying about Putin’s upper hand at the meeting in Hamburg.

“Rex Tillerson, a man who is ‘dumb as a rock’ and totally ill prepared and ill equipped to be Secretary of State, made up a story (he got fired) that I was out-prepared by Vladimir Putin,” the president tweeted. “I don’t think Putin would agree. Look how the U.S. is doing!”