National security adviser John Bolton on Sunday praised Sen. John McCain for supporting his nomination as UN ambassador but stopped short of calling for the White House to apologize to the Arizona Republican for ugly comments about his battle with brain cancer.

“He spent countless hours trying to help me out, and much of it was behind the scenes,” Bolton told CNN’s “State of the Union.” “There was no political upside for John McCain in that effort at all, but he did it because he thought I was being treated unfairly. I’ll never forget it, I’ll be grateful forever, and I wish John McCain and his family nothing but the best.”

But when asked if the White House should apologize after Kelly Sadler, a communications aide, dismissed McCain’s influence in opposing CIA nominee Gina Haspel by saying “he’s dying anyway,” Bolton hedged.

“Look, I wasn’t in that meeting, I don’t know what was said or what was done,” Bolton said. “I’ll just say this. John McCain, he came to my defense in 2005 when my nomination for the U.N. Ambassador was under criticism.”

Bolton, who was eventually installed as ambassador by a recess appointment by former President George W. Bush, stepped down in December 2006 when the temporary appointment expired.

Sadler apologized to McCain’s daughter Meghan McCain.

But White House Press Secretary Sarah Huckabee Sanders last Friday said she wouldn’t “validate a leak” of remarks made during a private meeting.