Sen. Bernie Sanders slammed the White House Sunday for failing to apologize for a staffer's cruel joke about Sen. John McCain, who has been battling brain cancer.

“It is one thing in the White House for somebody to say something crude and stupid and disrespectful about an American hero,” Sanders, an Independent from Vermont, said on CNN's "State of the Union." “It is another thing for them not to apologize.”

“It is beyond my comprehension,” he told host Jake Tapper. “And I just don't know what goes on in that White House mentality for there not being an apology for that terrible remark.”

Sanders said that while he and McCain have "strong differences of opinion," he is fond of the Arizona Republican.

"I personally like John very, very much," Sanders said. "He is very well respected in the Senate and in the country."

WHY: It was reported last week that White House aide Kelly Sadler said in a meeting that McCain’s opposition to President Donald Trump’s nominee for CIA director, Gina Haspel, was irrelevant because he is “dying anyway.”

McCain, a Republican from Arizona, ​who was tortured as a prisoner of war in Vietnam, has publicly opposed Haspel's nomination because of her involvement in the the CIA’s enhanced interrogation program during the George W. Bush administration.

Sadler reportedly called Meghan McCain to apologize for the comment about her father, but the White House has yet to directly address the matter.

White House press secretary Sarah Huckabee Sanders dodged questions about it in Friday’s press briefing, and other Trump administration officials dismissed the remark as a “bad joke" and complained that it was leaked. 

The Trump White House has a combative relationship with the press and has proved reluctant to concede to public pressure, whether to acknowledge Russian meddling in the 2016 election or fire staff secretary Rob Porter over allegations of domestic violence made by his ex-wives.