US congressional candidate Greg Gianforte has been charged after a reporter accused the Montana Republican of "body-slamming" him at a campaign event.
The Gallatin County sheriff's office issued the citation on Wednesday for misdemeanour assault, hours after Guardian correspondent Ben Jacobs said in a Twitter post and a television interview that Gianforte "body-slammed" him, breaking his glasses.
The incident in Bozeman happened when Jacobs sought to question Gianforte about healthcare, according to an audio tape captured by Jacobs and played on MSNBC and CNN.
Fox News reporter Alicia Acuna, who said she and her crew were in the room preparing to interview Gianforte, wrote that she saw Gianforte as he "grabbed Jacobs by the neck with both hands and slammed him to the ground".
Acuna, her field producer and photographer then "watched in disbelief as Gianforte began punching (Jacobs) as he moved to top of the reporter".
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Gianforte's campaign did not deny Jacobs' allegation but countered by saying Jacobs instigated the altercation by barging into the candidate's office, shoved a recording device in his face "and began asking badgering questions".
"After asking Jacobs to lower the recorder, Jacobs declined," campaign spokesman Shane Scanlon said.
"Greg then attempted to grab the phone that was pushed in his face. Jacobs grabbed Greg's wrist and spun away from Greg, pushing them both to the ground."
Acuna disputed that Jacobs was the aggressor.
Jacobs told MSNBC he retreated to a car park after the confrontation to call his editor and the police.
Gianforte faces a $US500 ($A667) fine and six months in jail if convicted.
In Jacobs' audio tape, Gianforte is heard shouting: "I'm sick and tired of you guys. The last guy who came here, you did the same thing."
After loud scuffling noises are heard, Gianforte repeatedly yells: "Get the hell out of here."
Jacobs is heard saying: "You just body-slammed me and broke my glasses."
According to the tape, the confrontation began as Jacobs tried to ask Gianforte if he supported a Republican healthcare bill after it was given a negative assessment by the Congressional Budget Office.
Gianforte is running against Democrat Rob Quist, a political novice who hopes to pull off a surprise victory in the Republican-leaning state.
A Quist win could signal trouble for President Donald Trump and his fellow Republicans as they defend their House majority in the 2018 mid-term elections.
