US Senator John McCain has denounced Republican presidential candidate Donald Trump for his attack on the parents of a Muslim US Army officer killed in the Iraq war.
The Arizona Republican waded on Monday into the dispute between his party's controversial nominee and Khizr and Ghazala Khan, issuing the strongest rebuke yet to Trump from a senior Republican on the issue.
"While our Party has bestowed upon him the nomination, it is not accompanied by unfettered license to defame those who are the best among us," wrote McCain, who was a prisoner of war for five years during the Vietnam War.
Mr Trump's dispute with the Khans has dominated the election campaign in recent days after Khizr Khan spoke at the Democratic National Convention on Thursday night, with his wife standing at his side.
Their son, Army Captain Humayun Khan, was killed by a bomb in Iraq in 2004, and the father spoke emotionally of the sacrifice his son had made for the country as an American Muslim, specifically criticising Mr Trump's proposal to ban Muslims from entering the country.
In response to the speech, Mr Trump said he had also made sacrifices in his life.
He also said that Ghazala Khan might not have been "allowed" to speak, implying her silence reflected restrictions placed on women by some traditional Muslims.
The parents said Mr Trump is ignorant about Islam and about their family's sacrifice.
Several leading Republicans have weighed in to express support for the family.
Mr Trump's off-the-cuff insults and controversial proposals such as the ban on Muslims and a plan to keep illegal immigrants out by building a wall along the Mexican border, have made many in the party establishment reluctant backers of his White House bid.
In his statement, Mr McCain recalled how Humayun Khan died, saying that when a suicide bomber aimed his vehicle toward a building housing hundreds of US soldiers, the captain told his subordinates to stay away, then ran toward it.
Mr McCain thanked the Khans for coming to America, saying "your son was the best of America, and the memory of his sacrifice will make us a better nation - and he will never be forgotten".
In remarks to television networks on Monday, Khizr Khan said Mr Trump lacked the empathy to be a leader and chided him for throwing the first salvo in their exchange.
Mr Trump responded simultaneously on Twitter to the parents' morning television appearances, saying he was being "viciously" attacked.
Mr Trump has tried to shift focus from the Khans.
"This story is not about Mr Khan, who is all over the place doing interviews, but rather RADICAL ISLAMIC TERRORISM and the US. Get smart!" Mr Trump said on Twitter.
Ghazala Khan wrote an opinion piece in The Washington Post on Sunday saying that she had remained silent during her husband's remarks to cope with making her grief public during the convention.
In their interviews on Monday, the Khans described the outpouring of support they have received during their very public exchange with Mr Trump.