Speaking on Friday night in Dimondale, Michigan -- a predominantly white suburb -- Trump lamented the collapse of American manufacturing and criticised free trade deals as he laced into rival Hillary Clinton and the Democratic Party, saying they were taking black voters for granted, CNN reported.
"You're living in poverty, your schools are no good, you have no jobs, 58 per cent of your youth is unemployed -- what the hell do you have to lose?" Trump asked the audience in an unscripted moment from a speech in which he otherwise stuck to his teleprompter.
He promised to "produce" for African-Americans where Democrats had failed.
"If you keep voting for the same people, you will keep getting exactly the same result," BBC quoted Trump as saying.
Trump also predicted he would receive 95% of the African-American vote if he went to on to run for a second term in 2020.
President Barack Obama, historically the most popular president among African-Americans in US history, received 93 per cent of the black vote in 2012, the BBC said.
Trump has suffered from dismal support among African-Americans.
Current polls showed about 2 per cent of black voters say they will vote for the New York real estate developer.
Friday's speech follows major changes in Trump's campaign. Earlier in the day, campaign chairman Paul Manafort resigned, and on Wednesday, Trump announced a new campaign manager and CEO, CNN added.