Terence Crawford has become the undisputed welterweight champion after a dominant performance against Errol Spence Jr in Las Vegas.

Crawford unleashed a flurry of punches in round nine to a wobbly Spence who could not defend himself, forcing the referee to step in and stop the fight.

It took just two rounds for Crawford to land his first of three knockdowns, with the next two coming in round seven.

Spence was brave throughout the bout, hanging on in a fight he was significantly behind in, but eventually Crawford took it out of his hands.

Crawford showed his respect to his downed opponent after the fight and said he would be up for a rematch.

"It was a good stoppage. I was on the verge. The referee did what he was supposed to do to protect the fighter," Crawford said.

"If the fight happens again I am pretty sure the support will come out again for both of us."