Washington - Donald Trump made a pitch to African-American voters on Tuesday, saying Democrats had "betrayed" them and pledged he would revitalise impoverished urban communities.His comments at a rally in the Midwestern state of Wisconsin came as something of a surprise from the Republican candidate who until now has done little to endear himself to minorities.With polls showing the bombastic billionaire trailing his White House opponent Hillary Clinton overall and in battleground states, it appeared Trump was trying to expand his support base beyond his core of working-class white voters."I'm asking for the vote of every African-American citizen struggling in our country today who wants a different and much better future. It's time for our society to address some honest and very, very difficult truths."The Democratic Party has failed and betrayed the African-American community."Black Americans tend to vote Democratic and Clinton has a solid lead among the demographic.But Trump said Democrats have "taken the votes of African-Americans for granted. They just assume they'll get your support and done nothing in return for it," he said."It's time to rebuild the inner cities of America and to reject the failed leadership of a rigged political system."Trump was speaking in West Bend following a spasm of racially charged violence over the weekend in Wisconsin's largest city of Milwaukee after police there shot dead a black man.Officials said the 23-year-old man was armed, but the death angered residents, as it echoes a series of deadly police incidents in the United States involving mainly African American suspects.BigotryTrump's outreach to black voters came after he said earlier on Tuesday that he would reject bigotry "in all forms" if elected president.It was another unexpected move from the Republican nominee who during his presidential campaign has vowed to ban Muslim immigrants and erect a wall to prevent Mexican immigration."This is my pledge to the American people: as your president I will be your greatest champion," Trump said in a statement posted on Facebook."I will fight to ensure that every American is treated equally, protected equally and honoured equally," he said."We will reject bigotry and hatred and oppression in all its forms, and seek a new future built on our common culture and values as one American people."