National security adviser John Bolton. (Mark Wilson/Getty Images)

John Bolton, President Trump’s national security adviser, praised Sen. John McCain on Sunday as a fair public servant but stopped short of offering an apology for a cruel remark by a White House communications aide about the Arizona Republican’s battle with brain cancer.

Bolton said he could not comment on the remark because he was not present when the aide, Kelly Sadler, told other communications aides at a closed-door staff meeting that McCain’s opposition to Gina Haspel as CIA director did not matter because “he’s dying anyway.”

Instead, Bolton said he remained grateful for McCain’s past support, particularly during his 2005 confirmation battle to be ambassador to the United Nations, a post for which Senate Democrats blocked Bolton before George W. Bush gave him an interim appointment.

McCain worked with other senators to try to win enough votes for Bolton to overcome a filibuster, at a time when Bolton’s political standing was not strong because the direction of the Iraq War was unpopular. He was a fierce advocate of the war.

“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,” Bolton said on CNN’s “State of the Union.”

McCain has been home in Arizona since mid-December as he battles an aggressive form of brain cancer. Sadler’s comment was prompted by McCain’s announcement on Wednesday that, if he is present in the Senate for Haspel’s confirmation vote later this month, he will vote against her because of her role in helping the “enhanced interrogations” of terrorism suspects held at secret CIA black sites in the wake of the Sept. 11, 2001, attacks.

A prisoner of war for 5½ years in Vietnam, McCain endured torture and has long opposed U.S. operatives engaging in such techniques, which he believes go against American values and are ineffective at obtaining accurate information.

Pressed by CNN’s Jake Tapper on whether he would apologize for Sadler’s remark, Bolton demurred.

“I’ve said what I’m going to say,” he said.

The Trump administration’s refusal to formally apologize for the McCain comment has angered Democrats and many Republicans who view the senator as a war hero. “Those who mock such greatness only humiliate themselves and their silent accomplices,” Mitt Romney, the 2012 Republican presidential nominee and a Senate candidate, tweeted Saturday.