Image copyright Pool Republican presidential nominee Donald Trump has said he will accept the results of the US election "if I win".
He added that he would accept a "clear" result - but reserved the right to challenge a "questionable" result.
He appeared at a rally in Delaware, Ohio, speaking for the first time since the third and final debate on Wednesday.
Mr Trump came under fire during the debate for suggesting that he might not accept the election's outcome.
When moderator Chris Wallace asked Mr Trump if he would accept a losing outcome to his Democratic rival Hillary Clinton, Mr Trump said he would "keep you in suspense".
Mr Trump's campaign manager, Kellyanne Conway, later insisted that the candidate had meant he would not concede until the "results are actually known".
The remark, which drew anger from some Republicans, is part of Mr Trump's repeated claim that the election is "rigged" against him.
Mr Trump told the Ohio audience that the election was posing questions about "the fairness of our country".
"I would like to promise and pledge to all of my voters and supporters and to all of the people of the United States, that I will totally accept the results of this great and historic presidential election - if I win," he said, grinning.
He later added: "I will accept a clear election result, but I will also reserve my right to contest and file a legal challenge in the case of a questionable result."
He also reiterated a claim he made during the debate against Mrs Clinton and President Barack Obama, who he said were responsible for inciting violence at a Chicago rally earlier this year.
The crowd erupted into cheers of: "Lock her up!"
He has faced damaging fallout after a video emerged of him making obscene remarks about groping women.
When asked to address the allegations made against him by several women in the wake of the video, Mr Trump said the claims had been "largely debunked".
Polls suggest Mrs Clinton is ahead nationally and in key battleground states.
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- US election glossary: A-Z guide to political jargon
Who is ahead in the polls?
51%
Hillary Clinton
41%
Donald Trump
See full poll trackerLast updated October 18, 2016