After shaking his hand and walking back up to the podium, Trump told the crowd: "Never wrestle him".
Gianforte pled guilty to a misdemeanor charge of assault and was sentenced to a 180-day deferred sentence, 40 hours of community service, 20 hours of anger management and a $300 fine along with a $85 court fee. I know Montana pretty well.
"Any guy that can do a body slam. he's my guy", he said to cheers and laughter at a rally in Montana.
Gianforte was captured on an audio recording physically assaulting Ben Jacobs, a reporter for the Guardian newspaper.
Trump was speaking at a rally in Missoula, Mont., where the president was campaigning for a Republican challenger to Sen.
"This will be an election of (Justice Brett) Kavanaugh, the caravan, law and order and common sense", Trump said.
It also came amid worldwide furor over the disappearance of journalist Jamal Khashoggi, last seen entering the Saudi consulate in Turkey earlier this month.
"Then I said, well, wait a minute".
Trump recalled that he was in Rome at the time of the incident, and he shared his initial thoughts: "This was awful".
In a statement, the Guardian's US editor John Mulholland said he hoped the president would apologise for his comments, adding: "To celebrate an attack on a journalist who was simply doing his job is an attack on the first amendment [of the US Constitution] by someone who has taken an oath to defend it".
"To celebrate an attack on a journalist who was simply doing his job is an attack on the First Amendment by someone who has taken an oath to defend it", he said, referring to the amendment to the United States constitution that guarantees freedom of the press.
Khashoggi, an outspoken critic of Saudi Arabia and its leader, Crown Prince Mohammed bin Salman, reportedly feared that his native county would retaliate against him.