Washington (AFP) - Family and congressional colleagues pushed back Friday against attacks on cancer-stricken John McCain, including one by a White House aide who reportedly said the senator's opposition to a presidential nominee did not matter because "he's dying anyway."

Amid rising bipartisan fury, the White House declined to apologize, or to acknowledge that the comments attributed by US media to White House communications aide Kelly Sadler were even made.

Sadler's apparent remark came after McCain announced his opposition to CIA director nominee Gina Haspel over her role in Bush-era enhanced interrogation techniques.

CNN quoted a White House official as saying Sadler, speaking Thursday at a staff meeting, meant the comment as a joke but that it flopped.

Another extraordinary attack against McCain by a fellow military veteran and commentator also stunned much of Washington, when retired US Air Force lieutenant general Thomas McInerney said he knows torture works because it made McCain spill sensitive information to his captors during his years as a prisoner of war in Vietnam.

"The fact is, with John McCain, it worked on John. That's why they call him Songbird John," McInerney said Thursday on Fox Business Network.

The attacks, remarkable for their bluntness, triggered swift reaction from across the political spectrum, with lawmakers demanding an apology from President Donald Trump.

"People have wondered when decency would hit rock bottom with this administration. It happened yesterday," said Democratic former vice president Joe Biden, who served with McCain for decades in the Senate.

"Given this White House's trail of disrespect toward John and others, this staffer is not the exception to the rule; she is the epitome of it."

Trump's press secretary offered no contrition when asked about the flap.

"I'm not going to validate a leak, one way or the other, out of an internal staff meeting," Sarah Sanders told reporters on Friday, as she insisted that Trump's pugnacious style does not set guidelines for White House discourse.

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"There is not a tone set here," Sanders said. "We have a respect for all Americans."

Sanders also confirmed that Sadler remained in her job.

Meghan McCain, a conservative commentator on ABC's popular morning talk show "The View," delivered an eloquent defense of her father, who is battling brain cancer at home in Arizona.

Her family, she said on the show, is "really strong" and "there's so much more love and prayer and amazing energy being generated towards us than anything negative at all."

She also had pointed words for the White House.

"I don't understand what kind of environment you're working in when that would be acceptable and then you can come to work the next day and still have a job," she said.

Her father is "all about character and bipartisanship and something greater than yourself," Meghan McCain said, before adding a stinging message to the critics: "Nobody's going to remember you."

- 'Moral failing' -

Members of Congress rallied behind their ailing, war-hero colleague.

"I am left speechless and with a sense of horror about the insensitive, crass and cruel remarks by a White House aide reflecting the administration's position on a heroic American's courageous fight," House Democrat Sheila Jackson Lee wrote.

Congressman Adam Kinzinger, a Republican and former US Air Force pilot in Iraq and Afghanistan, blasted Sadler.

"What was said yesterday goes beyond the pale; it's a moral failing and unacceptable," Kinzinger tweeted.

Over at Fox Business, program host Charles Payne issued a personal apology to McCain and his family, saying he did not initially hear McInerney's comment as the network's control room was speaking into his earpiece.

"I regret I did not catch this remark, as it should have been challenged," Payne said.

"As a proud military veteran and son of a Vietnam Vet these words neither reflect my or the network's feelings about Senator McCain, or his remarkable service and sacrifice to this country."

Trump, for his part, once mocked McCain's war service, saying during the presidential campaign that "I like people that weren't captured."