The Gold Star parent of a Muslim soldier slain in Iraq said he was “saddened all over again” by Donald Trump’s claims that if he had been president, his son would still be alive.

Khizr Khan, father of captain Humayun Khan, told CNN: “I was saddened all over again that this candidate lacks … the ability to understand the pain of those that had sacrificed their lives in defence of this country.

“In addition to that I want to salute and extend my deepest gratitude to all men and women that are serving today and have served before.”

His comments follow Mr Trump’s claim at the second presidential debate on Monday night in St Louis that he would not have ordered soldiers to go to Iraq.

“First of all, Captain Khan is an American hero, and if I were president at that time he would be alive today, because unlike her [Hillary Clinton], who voted for the war without knowing what she was doing, I would not have had our people in Iraq,” Mr Trump said.

“Iraq was disaster. So he would have been alive today.”

His stance was a turnaround from previous months when he criticised Mr Khan’s “nasty attacks” on him and also questioned his wife, Ghazala Khan, as to whether she was “allowed” to speak as she stood silently beside her husband on the stage at the Democratic National Convention.

Mr Trump’s claims that he never supported the Iraq War have been disputed as he told the Howard Stern Show more than a decade ago: “Yeah, I guess so”, when asked if he supported invading Iraq.

Mr Khan told CNN that more than 4,000 men and women died in Iraq. He accused Mr Trump of putting “political expediency” ahead of the “pain and suffering” of the families involved in the war.

“I said two months ago that this character does not have the character to be the commander in chief of the armed forces and my appeal to the Republicans has been and I repeated that they should have repudiated,” he said.

“We would not have been watching what is happening to the Republican Party [today].”

House speaker Paul Ryan told a GOP call on Monday that he would no longer defend Mr Trump for the next month following a leaked 2005 video in which the nominee was seen to brag about sexual assault and making lewd and vulgar comments about women.