Republican presidential candidate Donald Trump speaks to supporters at a rally on August 18, 2016 at the Charlotte Convention Center in Charlotte, North Carolina. (AFP photo)
US Republican presidential nominee Donald Trump has apologized for his past controversial comments that "may have caused personal pain" as he attempts to refocus his message in the face of falling opinion poll numbers.
Trump said on Thursday that he realized that his remarks, which have angered minorities and alienated large swaths of American voters, may have been ill-advised.
"Sometimes in the heat of debate and speaking on a multitude of issues, you don't choose the right words or you say the wrong thing. I have done that," Trump said at a rally in Charlotte, North Carolina.
"And believe it or not, I regret it, and I do regret it, particularly where it may have caused personal pain," he added.
Trump did not cite any examples of such comments. His campaign has been marked by controversy from the beginning, including disparaging remarks about women, Mexican immigrants and Muslims.
Trailing Democratic presidential nominee Hillary Clinton in national opinion polls, Trump has tried to rearrange his campaign. On Wednesday, he announced he was overhauling his campaign operation for the second time in less than two months.
In his remarks, the celebrity businessman delivered a new, inclusive tone and tried to appeal directly to non-white voters and urged African-American voters to give him a chance.
"I will not rest until children of every color in this country are fully included in the American Dream," Trump told his audience, again accusing Democratic Hillary Clinton of "bigotry."
Clinton's campaign dismissed the apology as just words he read from a teleprompter.
"Donald Trump literally started his campaign by insulting people. He has continued to do so through each of the 428 days from then until now, without shame or regret," said spokeswoman Christina Reynolds in a statement.