The 29-year-old Welshman remains undefeated and will now hope to go on and fight another American, the light-heavyweight champion Roy Jones Jnr.

Calazghe, Britain's longest reigning champion, floored his man twice in an outstanding demonstration of his talent.

He dropped the American in the third round with a ferocious left uppercut, although the challenger managed to beat the count

But the end was not long in coming, Calzaghe flooring McIntyre again at the start of the fourth round and this time the referee called a halt to proceedings.

The undefeated Calzaghe improved his record to 32 wins with 27 KOs, while McIntyre of Bogalusa, Louisiana, drops to 29 wins with three defeats with 13 KOs.

Calzaghe is now looking for a unification fight with WBC champion Eric Lucas of Canada, or the 1996 Olympic gold medallist David Reid.

In other significant action on the card, heavyweight Ray Mercer defeated Brian Scott by second-round knockout.

The 40-year-old Olympic gold medallist from 1988 is expected to fight WBO heavyweight champion Wladimir Klitschko next.