"Why doesn't he show his birth certificate? I really believe there's a birth certificate," Trump said Wednesday on ABC's "The View." "Why doesn't he show his birth certificate? I think he should. I think it's a terrible pall that's hanging over him."
So-called "birthers" question whether Obama was born in the United States.
Trump, who's considering whether to jump into the Republican battle to run for the presidency in 2012, said he wanted Obama to show his birth certificate, suggesting "there's something on that birth certificate he doesn't like."
The women on the daytime talk show spoke at once following that remark, making comebacks difficult to hear.
Trump said he will make a decision before June.
"I will do a good job," Trump said, quickly adding if he decides to run and "if I win."