Riyadh is suspected of murdering Khashoggi, a Washington Post contributor and United States permanent resident whose writings have been critical of powerful Saudi Crown Prince Mohammed bin Salman.
"This will be an election of (Justice Brett) Kavanaugh, the caravan, law and order and common sense", Trump said. But, Trump said he is "waiting for the results" of investigations being conducted by Saudi Arabia and Turkey, after which he pledged to make "a very strong statement".
Trump said that Gianforte had "nothing to be embarrassed about", imitating the action of slamming someone to the ground. "I know Montana pretty well", Trump said.
Gianforte pleaded guilty to a misdemeanor assault charge and was sentenced to 40 hours of community service and 20 hours of anger-management, in addition to the $385 in court fees and fines.
Trump later recalled his initial reaction to the attack, claiming that he thought it would help rather than hurt Gianforte's prospects.More news: China plans to replace streetlights with ‘artificial moon’ by 2020
Trump's remarks at a rally in Montana come amid an global outcry over the disappearance of Jamal Khashoggi, a journalist who has been missing since entering Saudi Arabia's consulate in Istanbul on October 2, whom the president has said is likely dead.
On Mr Biden challenging him to a fight, Mr Trump said, "He'd be down, faster than Greg would take him down".
Trump also recounted how he initially heard about the incident, and why he believed it to be good news for Gianforte's campaign as voters headed to the polls.
Gianforte won by a six-point margin in 2017, but still faces re-election this year. "We hope decent people will denounce these comments and that the President will see fit to apologize for them".