Bernie Sanders pledged to release his medical records Sunday.

The release became an issue on the campaign trail Saturday when Clinton surrogate David Brock called on the 74-year-old Sanders to release his medical records, only to be rebuffed by top Clinton campaign aide John Podesta. The Sanders campaign called Brock's call, "vile and desperate."

"Of course we're going to release our medical records," Sanders said Sunday. "It is not a problem."

"Thank God, I am very healthy," Sanders said.

Hillary Clinton has released medical records showing a clean bill of health, countering speculation by conservative pundits that the 68-year-old former secretary of state has undislosed medical problems.

Donald Trump has alleged she lacks the energy and stamina to be president.

Sanders would be the oldest person ever inaugurated as president of the United States. Ronald Reagan was inaugurated for the second time as president in 1985 at the age of 72.

Sanders attacked media claims that Brock is just a Clinton backer. Sanders argued Brock is much closer and more integral to the effort to get Clinton elected.

"David Brock is not a Clinton ally — he's head of their super [political action committee]," Sanders said.