Donald Trump's personal physician told NBC News it took him only five minutes to write a public letter last year attesting to Trump's "astonishingly excellent" health while a limo waited outside to deliver it to the GOP presidential nominee.

Dr Harold Bornstein's report in December remains the only medical information released so far by Trump's campaign.

In the letter, the doctor declared: "If elected, Mr. Trump, I can state unequivocally, will be the healthiest individual ever elected to the presidency."

Bornstein, who says he is board-certified in internal medicine and gastroenterology, has been Trump's doctor for 35 years. He told NBC News in an exclusive interview on Friday that he stood by his glowing assessment of the 70-year-old real estate magnate.