Donald Trump has been criticised after the Republican candidate refused to say whether he'd accept the results of the US presidential election.

Mr Trump has claimed in recent days that the presidential campaign is "rigged," and at Wednesday's debate in Las Vegas, he was asked whether he would accept the election results, no matter the outcome.

He refused to make that commitment, saying he would "look at it at the time."

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When pressed again by moderator Chris Wallace, the GOP nominee said: “I will tell you at the time. I will keep you in suspense.”

Mr Trump's statements drew criticism from members of both parties, including his opponent, Hillary Clinton, who said his position is "horrifying" during the debate.

Sen. Lindsey Graham, a GOP senator from South Carolina who has refused to back Mr Trump, said in a statement that the Republican nominee was "doing the party and country a great disservice by continuing to suggest the outcome of this election is out of his hands and 'rigged' against him. If he loses, it will not be because the system is 'rigged' but because he failed as a candidate."

House Democratic Leader Nancy Pelosi in a statement after the debate said that "just when you think you have seen it all from Donald Trump, he stoops to a new low with his contempt for the sanctity of our elections."

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Senate Democratic Leader Harry Reid tweeted that Trump must "immediately reverse course and say he will accept the results."

Conservative commentator Laura Ingraham, a Trump supporter, tweeted that "he should have said he would accept the results of the election. There is no other option unless we're in a recount again."

Steve Schmidt, a GOP strategist, told MSNBC that the answer was a "disqualifying moment" and represented a "clear and present danger to our constitutional order."

Nicolle Wallace, a NBC News analyst and an advisor to the 2008 McCain campaign, said on NBC of Trump's response: "He may as well have laid down in his own coffin with a hammer and nail and pounded it in himself."

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Carlos Curbelo, a GOP congressman from Florida, wrote on Twitter that the "acceptance of election results is fundamental to our democracy & Constitution. This cannot be undermined ever."

Meanwhile, some of Trump's most prominent supporters tried to clarify what the GOP nominee meant, including Sarah Palin, the 2008 Republican vice presidential nominee.

"If they're legit results, then of course they'll be accepted," she said.

The former Alaska governor added: "We accept the results of the election if they're fair."