Las Vegas: Joe Calzaghe didn't stop punching after a terrible start against Bernard Hopkins, and now the Pride of Wales is the best light heavyweight in the world.

Calzaghe won a split decision on Saturday night, desperately rallying in the final rounds against his cagey 43-year-old opponent to remain unbeaten in his long-anticipated debut in the United States.

Hopkins put on a master class in the veteran skills of their sport, knocking down Calzaghe with a sneaky right hand just 70 seconds in. But after floundering against Hopkins' defence through the early rounds, Calzaghe never stopped working and wearing down his older opponent, eventually gaining control of the final rounds.

Judge Ted Gimza scored it 115-112 for Calzaghe, and Chuck Giampa favored Calzaghe 116-111. Judge Adelaide Byrd gave it 114-113 to Hopkins, as did many reporters at ringside, who also favoured Hopkins despite Calzaghe's dominance in the final five rounds.

Calzaghe landed 33 per cent of his 707 punches, while Hopkins connected with 27 per cent of his 468 blows. Calzaghe had the edge in power punches with both total and accuracy, and he heavily outjabbed Hopkins

Calzaghe has been a super middleweight champion since 1997, winning 21 consecutive defences and adding two more belts last November with a unification victory over Mikkel Kessler. But the flying-phobic Welshman never found a match-up enticing enough to get him across the Atlantic Ocean to boxing's biggest stage.

Saturday's bout has been anticipated for at least six years by fight fans who craved its challenges and stylistic contrasts. After several false starts and disputes between the fighters' promoters, the bout gained steam last December when Hopkins and Calzaghe got into a shouting match one day before Floyd Mayweather's fight with Ricky Hatton.

"I would never let a white boy beat me. Never," Hopkins proclaimed, and Calzaghe quickly agreed to find out whether the Executioner was correct.