WASHINGTON — Donald J. Trump has refused again to acknowledge that President Obama was born in the United States, reviving the so-called birther issue that the Republican presidential nominee has played down since announcing his campaign last year.

The resurfacing of Mr. Trump’s doubts about Mr. Obama’s birthplace — in an interview with The Washington Post that was published on Thursday — comes less than two months before the general election and as he has been working more aggressively to court minority voters.

Late Thursday, in an effort at damage control, a Trump spokesman issued a statement saying that “Mr. Trump believes that President Obama was born in the United States.”

But the statement, by Jason Miller, a senior communications adviser, goes on to falsely blame Hillary Clinton for starting rumors about Mr. Obama’s birth in the 2008 campaign, and it then called her “weak” for not getting the question answered.