Ukraine`s Wladimir Klitschko knocked out previously unbeaten American Calvin Brock in the seventh round to retain the International Boxing Federation heavyweight world title, according to AFP.

Klitschko, considered the best of a lackluster collection of heavyweight champions, started slowly but came alive in the fifth round of their scheduled 12-round bout, punishing Brock with his stinging left jab.

Brock, who had settled down after a skittish first round to land some solid body blows in the earlier rounds, couldn`t find a way to get to the energized champion, who suffered a bloody cut over his left eye from an accidental head butt in the sixth.

Klitschko didn`t have to spend much time worrying if the cut would prove a factor in the outcome.

The champion hurt Brock repeatedly in the seventh before felling him with massive right that saw Brock fall face down on the canvas. He managed to rise, but referee Wayne Kelly waved it off at 2:10 of the round.

"It took me time to get my rhythm and distance," Klitschko said.

Brock was trying to follow the lead of fellow American Shannon Briggs, who defeated Sergei Liakhovich last Saturday to claim the lightly regarded World Boxing Organization heavyweight title.

"He had a better jab than I thought," Brock admitted. "I saw the punch coming, but couldn`t get out of the way. He`s the best fighter I have ever fought."

Klitschko, who was making the first defence of the title he won with a seventh-round stoppage of Chris Byrd on April 22, improved to 47-3 with 42 knockouts while Brock fell to 29-1.

After the bout, Klitschko reiterated his desire to unify the title.

"I will fight anybody with a belt," he said of his preferred next opponent.

Nicolay Valuev holds the World Boxing Association crown while Oleg Maskaev owns the World Boxing Council version of the title.

On the undercard, undefeated Laila Ali, daughter of legendary former heavyweight champ Muhammad Ali, made her Madison Square Garden debut with a fourth-round stoppage of Shelley Burton.

Her father watched from ringside giving a wave to acknowledged an ovation from the Garden Crowd.

Laila Ali had too much experience and power, improving to 23-0 with 20 wins inside the distance when the fight was stopped with two seconds left in the fourth.

"I`m on a high fighting here," she said. "It feels great to be fighting in front of my father."