Council on Foreign Relations president Richard Haass slammed Secretary of State Rex Tillerson in a tweet on Wednesday, calling for him to step down from the nation’s top diplomatic post.

“Rex Tillerson has been dealt a bad hand by the Potus & has played it badly. For both reasons he cannot be effective SecState & should resign,” the think-tank’s president said. 

Rex Tillerson has been dealt a bad hand by the Potus & has played it badly. For both reasons he cannot be effective SecState & should resign

— Richard N. Haass (@RichardHaass) October 4, 2017

Haass’s comments come as tensions appear to mount between Trump and Tillerson. 

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NBC News reported on Wednesday that Tillerson had mulled leaving his post this summer, and that top Trump administration officials, including Vice President Pence, urged him to stay in his post despite his growing frustration with Trump. 

State Department spokesman R.C. Hammond disputed the report, telling the network that Tillerson never considered quitting this summer. 

The president tweeted on Sunday that his Secretary of State was “wasting his time” trying to engage in direct talks with the North Korean leader Kim Jong Un.

I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man…

— Donald J. Trump (@realDonaldTrump) October 1, 2017 

…Save your energy Rex, we’ll do what has to be done!

— Donald J. Trump (@realDonaldTrump) October 1, 2017

The White House said Monday that President Trump has confidence in Tillerson, despite the president’s tweets.

“He does, yes,” White House press secretary Sarah Huckabee Sanders said when asked if Trump still has confidence in his State Department head.

Sanders said she believed the two men had spoken in the past day.