Donald Trump has refused to say whether he will accept the result of the US presidential election if he loses.
This comes after his clash with Hillary Clinton in their last head-to-head debate in Las Vegas ahead of the polls opening on November 8th.
Trump was questioned about claims he made ahead the debate, suggesting that the election is rigged in favour of his Democratic rival.
Asked by moderator Chris Wallace whether he would accept the election result, Mr Trump replied: "I will tell you at the time. I'll keep you in suspense."
Clinton described Trump's remarks as "horrifying", while the Republican National Committee said the national party would "respect the will of the people".
Clinton said: "Every time Donald thinks things are not going in his direction, he claims whatever it is is rigged against him.
"There was even at time when he didn't get an Emmy for his TV programme three years in a row and he started tweeting the Emmys were rigged against him."
Another tense exchange mentioned Vladimir Putin. The Democratic candidate branded Trump a "puppet" of the Russian president and challenged him to condemn Russia's suspected involvement in email hacking during the campaign.
"I don't know Putin," Trump said. "He said nice things about me. If we got along well, that would be good.
"He has no respect for her [Clinton] . He has no respect for our president.
Clinton responded: "That's because he'd rather have a puppet as president of the United States".