The New York Times reported three weeks ago that Mr Trump had said Haitians "all have Aids" during a June meeting about immigration.
A backlash to his latest alleged remarks was swift.
Elijah Cummings, a Maryland Democratic lawmaker, tweeted: "I condemn this unforgivable statement and this demeaning of the office of the Presidency."
Another black Democratic lawmaker, Cedric Richmond, said Mr Trump's comments "are further proof that his Make America Great Again agenda is really a Make America White Again agenda".
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