LAS VEGAS -- Even Mike Tyson would have been impressed.

	Obed Sullivan lasted only 51 seconds against No. 1 heavyweight contender David Tua.

Fighting with the savage explosiveness of the former heavyweight champion, David Tua needed only 51 seconds Saturday night to stop Obed Sullivan and firmly establish himself as the heavyweight division's leading challenger.

Three lefts in succession put Sullivan on the canvas in his corner, where he was counted out by referee Joe Cortez before the fans at the MGM Grand hotel-casino had settled in their seats.

"I knew it would be over when I caught him," Tua said.

Sullivan, a veteran who had never been stopped before the ninth round, appeared to flinch at the opening bell and quickly walked into a series of big punches.

He appeared stunned by the first left, then was finished off by a left uppercut that put him on the canvas.

"I'm more embarrassed than anything," Sullivan said. "I'm not sure how devastating a puncher he is because he caught me so cold."

Tua, the New Zealander ranked No. 1 by the International Boxing Federation and in line to face heavyweight champion Lennox Lewis by November, thrilled the crowd with his quick performance.

The 5-foot-10 Tua weighed 252 pounds, 14 more than any of his previous fights, in stopping his 12th opponent in the first round.

"Brother, I'm not a lightweight, I'm a heavyweight," Tua said. "I've been experimenting with my weight and I'm very comfortable with my weight."

Tua (36-1, 31 knockouts) fights much like Tyson, using his quick hands and explosive power inside to dominate opponents. He also seems to intimidate opponents, much like Tyson.

"He's a good soldier, a great warrior," Tua said of Sullivan, a former Marine. "But I had no doubt he was going down."

Sullivan, of Phoenix, fell to 35-7-1. He weighed 232 pounds.

Tua had said before the fight he would make quick work of Sullivan and then take Evander Holyfield's place in the WBA heavyweight title fight with John Ruiz that Holyfield pulled out of with an injury last week.

In another fight, Ben Tackie of Ghana was trailing badly when he unleashed a savage left hook early in the 10th round to stop former IBF junior lightweight champion Roberto Garcia.

Garcia dominated the lightweight fight with sharp combinations and seemed well in control when Tackie (20-1, 12 knockouts) caught him with an overhand right in the ninth round to score the first knockdown of the fight.

Garcia, of Oxnard, Calif., came back to land well at the end of the round, but he made the mistake of trying to trade punches with Tackie in the final round and Tackie caught him with a left hook that sent Garcia sprawling to the canvas on his back.

Garcia (32-2) got up but was bleeding and wobbly and referee Richard Steele stopped the fight at 35 seconds of the 10th round.