Donald Trump has been widely condemned after he mocked a dead US Muslim soldier's mother.
Ghazala Khan stood alongside her husband Khizr as he attacked the Republican presidential candidate in a powerful speech at the Democratic National Convention.
The couple's son Humayun was killed by a car bomb in 2004 while serving in Iraq. He was just 27.
Trump, who has proposed a ban on Muslims entering the US, responded by claiming Mrs Khan was not allowed to speak.
"If you look at his wife, she was standing there," he told ABC.
"She had nothing to say - maybe she wasn't allowed to have anything to say. You tell me."
Trump's remarks immediately sparked outrage, with many accusing him of attacking a grieving mother
Ex-US President Bill Clinton said: "I cannot conceive how you can say that about a Gold Star mother."
Democratic vice-presidential nominee Tim Kaine said it proved Mr Trump was unfit to be president.
Some Republicans also criticised their own presidential candidate.
John Kasich, Mr Trump's former rival for the Republican nomination, tweeted that the Khans should be treated with "honour and respect".
Ghazala Khan, who said she did not speak because she was still overwhelmed with grief, said she was upset by Mr Trump's comments.
"When I was standing there, all of America felt my pain, without a single word - I don't know how he missed that," she told ABC.
"Please Mr Trump, feel that pain and you will be better. I was upset when I heard that I didn't say anything because I was in pain."
Khizr Khan said Mr Trump was "devoid of feeling the pain of a mother who has sacrificed her son".
"Running for president is not an entitlement to disrespect... a Gold Star mother, shame on him," he said.
"He has no decency, he has a dark heart."
Mr Trump's campaign team released a statement on Saturday night - in a bid to limit the damage - in which he praised Mr Khan's son but rejected his criticism.
"Captain Humayun Khan was a hero to our country and we should honour all who have made the ultimate sacrifice to keep our country safe."
He added: "While I feel deeply for the loss of his son, Mr Khan who has never met me, has no right to stand in front of millions of people and claim I have never read the Constitution, (which is false) and say many other inaccurate things."
Mr Trump also told ABC that he had made "a lot of sacrifices" after Mr Khan claimed the businessman had sacrificed "nothing and no-one" for his country.
"I work very, very hard. I've created thousands and thousands of jobs, tens of thousands of jobs, built great structures. I've had tremendous success. I think I've done a lot."