Clinton said Trump's comments were more consistent with what dictators in non-democratic countries might say about their opponents.
Clinton, a former secretary of state, said Trump's comments were more consistent with what dictators in non-democratic countries might say about their opponents.
"To say you won't respect the results of the election, that is a direct threat to our democracy," Clinton told a rally at the University of North Carolina at Charlotte. "The peaceful transfer of power is one of the things that makes America America."
"And look, some people are sore losers, and we just got to keep going," she added.
Earlier on Sunday, Kellyanne Conway, a top Trump adviser, acknowledged that the Republican presidential candidate was lagging behind Clinton ahead of the election.
Conway said Clinton had "tremendous advantages," including a large campaign war chest that had allowed her to spend millions on television ads.
"We are behind," Conway said on NBC's "Meet the Press." But she added the Trump campaign was looking to sway undecided voters not ready to support Clinton.
As the polling gap has widened, Trump has said repeatedly the election is being "rigged" against him. He has not offered evidence and numerous studies have shown that the U.S. election system, which is decentralized and run by the states, is sound.
At last week's debate with Clinton in Las Vegas, Trump was asked if he would honor the result of the U.S. election.
"What I'm saying is that I will tell you at the time. I'll keep you in suspense. OK?" Trump said.