Terence Crawford retained his welterweight world title and remained undefeated with a sixth-round TKO after Amir Khan could not continue following an accidental low blow.

The blockbuster bout in New York came to an anti-climactic end after a shot below the belt left Khan unable to carry on against the WBO holder on Saturday.

While the crowd were left disappointed amid a chorus of boos, Crawford improved to 35-0 after the bout ended at the 0:47 mark.

"I could tell I was breaking him down," Crawford said inside the ring. "It was just a matter of time. I just took my time. I was disappointed the corner stopped the fight in that manner, but Virgil [Hunter] is a great coach, and he was looking out for his fighter. I know he didn't want to go out like that."

Crawford – rated one of the best pound-for-pound boxers in the world – was on the front foot following in the opening round, which saw the unbeaten boxer drop Khan in New York.

Khan landed a couple of jabs but Crawford suddenly caught the Brit with a counter right with a minute remaining – flooring his opponent.

Crawford almost sent former unified light-welterweight champion Khan to the canvas again before the bell rang and the 32-year-old dug deep from that point.

Khan was more defensive in the second as he struggled to find an opening, though he lunged with a lead left hook that Crawford took well.

Crawford – who switched to a southpaw stance – waited patiently for the killer blow and he made some inroads in the fourth, targeting the body as he stalked Khan.

The 31-year-old Crawford broke down Khan with more heavy hitting in the fifth and the fight came to a premature end a round later as the latter's corner informed the referee that their boxer could no longer continue.