The father of a Muslim soldier killed in Iraq protecting his base from a vehicle packed with explosives has called on Republican grandees to denounce Donald Trump.

Khizr Khan, father of U.S. Army Captain Humayun Khan, said House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell have a 'moral imperative' to tell Trump 'enough'.

Calling Ryan and McConnell 'decent human beings', he begged through tears for both men to take an 'ethical stand', saying Trump will 'sink the ship of the patriot Republicans.'

Khan also repeated his accusation that Trump has 'sacrificed nothing' for America, despite the billionaire suggesting that he has 'made a lot of sacrifices' through his businesses.

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Khizr Khan, father of U.S. Army Captain Humayun Khan, appeared alongside wife Ghazala to implore Paul Ryan and Mitch McConnell to speak out against Republican presidential nominee Donald Trump

Speaking on MSNBC's 'Last Call With Lawrence O'Donnell' on Friday, Khan said: 'If your candidate wins and he governs the way he has campaigned, my country, this country, will have constitutional crises [like] never before.

'There is so much at stake, and I appeal to both of these leaders: This is the time.

'There comes a time in the history of a nation where an ethical, moral stand has to be taken regardless of the political costs.

'The only reason they're not repudiating his behavior, his threat to our democracy, our decency, our foundation, is just because of political consequences.'

In a statement released on Saturday, Khan took aim again at Trump - over the presidential candidate's comments during an interview to be aired Sunday on ABC's This Week with George Stephanopoulos.

In the interview, Trump said: 'His wife... If you look at his wife, she was standing there. She had nothing to say.

'She probably, maybe she wasn't allowed to have anything to say. You tell me. But a plenty of people have written that. She was extremely quiet, and it looked like she had nothing to say.'

The Khan family told ABC News that 'running for president is not an entitlement to disrespect Gold Star families and a Gold Star mother'.

Khan's call to the GOP grandees comes days after he delivered a standout address to the DNC, brandishing a copy of the Constitution and asking if Trump 'has even read it'

Khan's son, U.S. Army Captain Humayun Khan, was killed defending his base in Iraq back in 2004

'Shame on him! Shame on his family!' Khan said.

'He is not worthy of our comments. He has no decency. He is void of decency, he has a dark heart.'

Ms Khan went on to say that she's sorry Trump doesn’t understand their faith.

'I don't know what type of Islam he has read or heard. I'm so sorry about that, that he has not had any idea what the Islam is,' she said.

'My faith, Islam, has given us strength, all the woman and man are equal in God's eyes. We are equal, we are the part of our husbands, they are the part of us. We can tell them what to do, they can tell us what to do.'

Trump released a statement praising Khan's son, after backlash over his earlier remarks.

'Captain Humayun Khan was a hero to our country and we should honor all who have made the ultimate sacrifice to keep our country safe,' the statement begins.

'The real problem here are the radical Islamic terrorists who killed him, and the efforts of these radicals to enter our country to do us further harm.

'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. If I become President, I will make America safe again.'

Khan's latest comments comes just days after he delivered one of that standout speeches of the Democratic National Convention.

During his highly emotional speech he pulled a copy of the Constitution from his pocket before asking Trump: 'Have you ever even read it?'

Asked about his view of the Republican nominee on Friday, he reiterated: 'He has done nothing. No sacrifice.

'He may be a wonderful father, but he is not suitable, not fit, even for the candidacy of the stewardship that he is seeking.'

For his own part, Trump has attempted to brush the speech aside, while contending that he has made sacrifices in his life.

Trump told ABC: 'I think I've made a lot of sacrifices. 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.'

The presidential nominee also insinuated that Khan's wife Ghazala was 'not allowed' to speak because of her faith.

He added: 'His wife... if you look at his wife, she was standing there. She had nothing to say.

'She probably, maybe she wasn't allowed to have anything to say. You tell me.'

However, in the same MSNBC interview, Ghazala explained her silence, saying she is unable to control her emotions on seeing pictures of her son, and so felt she couldn't address the audience.

Hillary Clinton came to her defense on Saturday afternoon after Trump's comments to ABC.

Khan called to both Ryan and McConnell 'decent human beings', but said 'this is the time' to take a moral stand against Trump, saying he will 'sink the ship of the patriot Republicans'

She said in a statement: 'I was very moved to see Ghazala Khan stand bravely and with dignity in support of her son on Thursday night. And I was very moved to hear her speak last night, bravely and with dignity, about her son's life and the ultimate sacrifice he made for his country.

'This is a time for all Americans to stand with the Khans, and with all the families whose children have died in service to our country,' Clinton said. 'And this is a time to honor the sacrifice of Captain Khan and all the fallen. Captain Khan and his family represent the best of America, and we salute them.'

As Khan spoke to the DNC earlier this week, a huge picture of the couple's son was projected on to the screen behind them.

Ryan and McConnell have found themselves at odds with Trump both during primary season and after he became the presumptive Republican nominee, endorsing him one minute and then casting doubt on him the next.

Ryan has been particularly vocal against some of Trump's most high-profile pledges, including the Muslim ban, which he has repeatedly knocked down as going against the values of conservatism.

The speaker has also rebuked Trump for appearing to encourage violence at his rallies, for questioning the bias of Judge Gonzalo Curiel based on his race, and for refusing to immediately denounce the support of white supremacist leader David Duke.

Both Ryan and McConnell have offered their support to Trump, despite remaining loudly critical of his behavior on the campaign trail and policies such as the Muslim ban

Despite the apparent gulf of opinions between the two, Ryan has officially endorsed Trump and has helped to unify the Republican party around their candidate following a bruising primary season.

Meanwhile McConnell has said Trump 'needs to change' before he is ready for the presidency, while praising Hillary Clinton as 'intelligent and capable'.

Speaking to Time Warner Cable news last month, McConnell said: 'Trump clearly needs to change, in my opinion, to win the general election.

'My hope is that he is beginning to pivot and become what I would call a more serious and credible candidate for the highest office in the land.'

Asked whether Trump met the 'threshold of credibility' to become President, McConnell added: 'He’s getting closer. Getting closer.'