Donald Trump accidentally fat-shames one of his supporters

US President Donald Trump mistook a supporter of his to be a protester at a rally on Thursday, and began taunting him about his size.

"That guy's got a serious weight problem," the US President told supporters in New Hampshire. "Go home. Start exercising. Got a bigger problem than I do. Got a bigger problem than all of us. Now he goes home and his mom says, 'What the hell have you just done?"

After the rally, Trump found out the man - Frank Dawson - was a supporter, and called him from Air Force One, as he flew from Manchester to New Jersey, where he is on a working vacation. A senior administration official said Trump could not reach Dawson but left the man a voicemail.

Fox News Channel's Fox & Friends show contacted Dawson, who said he was not upset by Trump's comment about his weight.

"I think he thought I was part of [the protest] but I wasn't. I was the good part of it," he said. "Everything's good. I love the guy. He's the best thing that ever happened to this country."

Trump, true to form, did not apologise for the comments, an aide confirmed to the New York Times.

Reuters / Newshub.