Donald Trump's personal physician told NBC News he needed just five minutes to write a glowing public assessment of Trump's health as a limousine waited to carry the letter back to Trump.

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

In it, he wrote: "If elected, Mr. Trump, I can state unequivocally, will be the healthiest individual ever elected to the presidency."

He also referred to the Republican candidate's health as "astonishingly excellent."

Asked to justify that statement, the doctor told NBC News: "I like that sentence, to be quite honest with you, and all the rest of [the presidents] are either sick or dead."

While he wrote last year that Trump's physical strength and stamina are extraordinary, Bornstein told NBC that he doesn't think Trump, 70, is in any better or worse shape than the average person who exercises daily.

Trump and his allies have been questioning the health of his Democratic rival, Hillary Clinton. Her physician has said the former secretary of state has no serious issues.

With files from CBC News