LONDON -- Vladimir Klitschko floored Monte Barrett in the opening round but then lumbered to an unimpressive seventh-round stoppage victory Saturday in pursuit of his bid for a world title fight.

The towering Ukrainian looked set for an early knockout win to go with the other 31 on his 33-1 previous record. But he failed to follow up the opening round salvo with any more impressive punching until the seventh round when he floored the American three times more and the fight was stopped at 2 minutes, 42 seconds. It was Barrett's second loss against 23 wins.

The fight was on the undercard of the Lennox Lewis-Frans Botha fight -- Lewis stopped Botha in the second round to retain his WBC and IBF world heavyweight titles -- and Klitschko did little to indicate he will be joining them soon.

Outweighing his opponent by 23 pounds and at least three inches taller, Klitschko wobbled Barrett with a short left in the middle of the opening round and, staggering onto the ropes, the American went down under lefts and rights for an eight count.

Klitschko also put Barrett down in the fourth with a slap combination that had the American rolling across the canvas. But the contest then developed into a mauling muddle in which the Ukrainian, watched by Lewis' fans at London Arena, failed to unload.

He finally found his range again early in the seventh with a short right hand which put Barrett down. Another right floored the American and finally a left-right combination prompted referee Richie Davies to halt the fight.

Also on the undercard, Adrian Stone, based in Paterson, N.J., but English born, had fellow Briton Geoff McCreesh down three times before scoring a fifth-round stoppage victory to hold on to his lightly regarded IBO light-heavyweight title.

Stone floored McCreesh with a short left hook 10 seconds into the second round and then had the challenger down on his knees again with a right-left.

A Stone right hand had McCreesh in trouble again in round five and he also opened up a cut above his opponent's left eye.

After another right hand put McCreesh down early in the fifth, Stone staggered him toward the end of the round and the referee moved in to stop the fight at 2 minutes, 32 seconds.

Noel Wilders held on to his IBO world bantamweight title, gaining a unanimous decision after a thrilling 12-rounder against fellow Englishman Paul Lloyd. Wilders was cut early in the fight but rocked Lloyd with a right hand in the fifth and ran out a clear winner on the judges' cards.

Veteran American Tom "Boom Boom" Johnson lost a unanimous decision to British fighter Scott Harrison in a 12-round IBO Intercontinental contest.