The neighbor accused of tackling the US senator Rand Paul while he was mowing his lawn faces a possible prison sentence after he pleaded guilty on Friday to the attack that left the politician with broken ribs and damaged lungs.

Rand’s longtime neighbor, Rene Boucher, admitted in a federal court in Kentucky to assaulting a member of Congress resulting in personal injury.

The episode had been “profoundly embarrassing” for Boucher, his lawyer, Matt Baker, said.

A judge set sentencing for 15 June. Federal prosecutors plan to seek a 21-month prison sentence, while the defense will argue for probation. The charge carries up to 10 years in prison and a $250,000 fine.

Paul was attacked on 3 November 2017, while mowing his lawn at his home in Kentucky. A friend of Paul’s said the senator had alighted from his ride-on lawnmower to remove a tree branch when he was suddenly tackled from behind. He suffered six broken ribs.

Boucher initially pleaded not guilty and Baker was keen for his client to avoid a federal charge. At the time, he said: “It has nothing to do with politics … it has to do with a disagreement between two neighbors.”

A staffer with Paul’s office disputed media reports that Paul or his wife Kelley had any “longstanding dispute” with their neighbor.

“The Pauls have had no conversations with him in many years,” senior adviser Doug Stafford said last year. “The first ‘conversation’ with the attacker came after Senator Paul’s ribs were broken. This was not a fight, it was a blindside, violent attack by a disturbed person.”

Boucher agreed to a plea deal in January. Before Friday’s hearing, he had spoken to the authorities of annoyance over Paul’s landscaping and a large pile of brush on his neighbor’s property, and had admitted to law enforcement officers that he ran on to Paul’s property and tackled the politician while he was not looking.

Baker will ask the court for mercy and leniency for his client at the time of sentencing, it was reported on Friday.