With Hillary Clinton sidelined by pneumonia, U.S. President Barack Obama took up the Democrats' fight against Donald Trump on Tuesday, trying to quash the Republican presidential candidate's bid to appeal to working-class voters.

Donald Trump criticized Hillary Clinton for her characterization that half of his supporters belonged in "a basket of deplorables," and suggested it makes her unfit for US presidency.

Hillary Clinton said Saturday that she was wrong to put half of Donald Trump's supporters in a "basket of deplorables," but didn't back down from a description of his campaign the Republican nominee said smeared many Americans and would take a political toll.