A top Senate Republican said there are three key Cabinet officials who are keeping President Donald Trump’s administration from sending the nation into “chaos.”

Sen. Bob Corker (R-TN), who hasn’t been afraid to speak his mind about Trump or his administration lately, told reporters Wednesday that Secretary of State Rex Tillerson, Secretary of Defense James Mattis, and Chief of Staff Gen. John Kelly are “those people that help separate our country from chaos,” whereas others in the administration act without considering national security.

Corker, the chair of the Senate Foreign Relations Committee who last month announced he would not run for reelection in 2018, was responding to a question about Tillerson’s rumored desire to resign from the administration.

“I deal with people throughout the administration, and [Tillerson], from my perspective, is in an incredibly frustrating place,” Corker said. “[Tillerson, Mattis, and Kelly] act in a very — they work very well together to make sure the policies we put forth around the world are sound and coherent, and there are other people within the administration whom I believe don’t.”

He went on to say those three top Trump officials are key to the “national security of our nation.”

Tillerson held an unscheduled press conference Wednesday morning in response to an NBC report that he had previously called Trump a “moron” and wanted to quit by July. The secretary of state, who has repeatedly been publicly undermined on foreign dealings in the Middle East and with North Korea, denied the report and said he had no intention of resigning.

Corker said he would not go into details of his private conversations with Tillerson but said he could see why the secretary would be frustrated.

“As I watch, and I can watch very closely in many occasions, [Tillerson] ends up not being supported in the way I would hope a secretary of state would be supported,” Corker said. “I have no knowledge of the comments or anything else. I think he’s in a very trying situation, trying to solve many of the world’s problems, a lot of times without the support and help that I’d like to see him have.”

This isn’t the first time Corker has said Trump and his administration could risk the nation’s security. In August, he said that “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,” adding that Trump’s lack of understanding of America’s “character” could put the nation “through great peril.”

He recently told reporters that he stands by those statements — and from the sound of his comments Wednesday, he is also willing to expand on them.

Watch Corker’s full comments here: