U.S. Rep.-elect Greg Gianforte of Montana will plead guilty to assaulting a reporter the day before being elected the state's only congressman last month, a prosecutor said on Friday.

The Republican technology entrepreneur will enter his plea in court on Monday, when he is scheduled to be arraigned and sentenced on the misdemeanour charge, Gallatin County Attorney Marty Lambert told The Associated Press.

Gianforte requested the court hearing after reaching a civil settlement this week.

Guardian reporter Ben Jacobs over claims that Gianforte knocked Mr Jacobs to the ground when the reporter asked him a question May 24.

As part of the settlement, Mr Jacobs said he would not object to Gianforte entering a plea of no contest, or nolo contendere, meaning Gianforte would concede to the charge without admitting guilt.

But Mr Lambert said Gianforte will plead guilty.