A top Senate Republican said Thursday that President Donald Trump’s instability and incompetence risks putting America “through great peril.”

Sen. Bob Corker (R-TN), chair of the Senate Foreign Relations Committee, told reporters at a town hall that “the president has not been able to demonstrate the stability” to be successful.

Corker referenced Trump’s response to the recent white supremacist violence in Charlottesville, Virginia, saying Trump “had not appropriately” addressed America on the incident. He also rebuffed the president’s recent attacks on Sen. Jeff Flake (R-AZ), calling Flake one of the best senators he knows.

According to USA Today, Corker leveled extraordinary criticism at the president during a Rotary Club meeting in Chattanooga, saying there had to be “radical changes” at the White House:

The president has not yet been able to demonstrate the stability, nor some of the competence, that he needs to demonstrate in order for him to be successful — and our nation and our world needs for him to be successful, whether you are Republican or Democrat. He also recently has not demonstrated that he understands the character of this nation. ... He has not demonstrated that he understands what has made this nation great and what it is today. And he’s got to demonstrate the characteristics of a president who understands that. Without the things I just mentioned happening, our nation is going to go through great peril. ... I think in spite of the fact that people are polarized in our nation right now, people have to understand that we should hope that (Trump) aspires, that he does some self-reflection, that he does what is necessary to demonstrate stability, to demonstrate competence, to demonstrate that he understands the character of our nation and works daily to bring out the best in the people of our nation.

Corker didn’t vow to take any concrete action to ensure that Trump doesn’t put America in “great peril.” For a list of options he may want to pick from, Vox’s Matt Yglesias has prepared seven of them right here.