BERLIN  - Undisputed world heavyweight champion Wladimir Klitschko claimed the 50th knock-out and 57th victory of his career when he ended hapless Frenchman Jean-Marc Mormeck's hopes in the fourth round on Saturday.

Klitschko, 35, defended his IBF, IBO, WBO and WBA titles against Mormeck, who stepped up from cruiserweight just over two years ago, in Dusseldorf and made good on his promise to knock the Frenchman out. "I'm delighted to get the 50th knock-out of my career, I promised and I delivered," said Klitschko, who had a 17cm height advantage over the Frenchman.

His elder brother Vitali, who was in his corner, confirmed he will defend his WBC title against Britain's ex-WBA champion David Haye this summer, but did not give a date or location. Mormeck, who turns 40 in June, was lucky to finish the second round after Klitschko put him on the canvas with 80 seconds left in the round with a firm right to the chin and then pinned him in a corner with a rapid combination.

The challenger was offering only token resistance and made a mockery of his pre-fight promises to smash Klitschko's "glass jaw" which was as ineffective as the handful of punches he threw in the opening rounds. The pair both ended on the canvas in the third after a slip, but it was all over in the fourth when a swift combination from the champion saw the Frenchman drop his guard and a final head shot left Mormeck on the canvas.

Puerto Rico referee Luis Pabon stepped in quickly to count out the fight at one minute and 12 seconds as the Frenchman lost his fourth fight in the heavyweight division. The pair were scheduled to meet last December, but kidney stones forced Klitschko to postpone the original fight and the ease of the champion's win will have done little answer the critics who said he had picked an easy fight.

After the fight, Mormeck explained his lack of urgency because of a cold he suffered in the build-up. "He knocked me out, yeah, ok, but he's hard to box because he is so tall and the referee should have stepped in more as he kept pushing me down, so I am quite frustrated," said the Frenchman.

Meanwhile, Klitschko has issued a warning to any fighters looking to step up to the heavyweight division to think twice after he knocked out Jean-Marc Mormeck. The champion said promising cruiserweights and light heavyweights to carefully consider any challenge for a world heavyweight title.

"I think all the light heavyweights who have ambitions to get into heavyweight division should think twice," he said, having claimed the 57th win of his career with just three defeats in 60 fights. "Jean-Marc wanted to believe I was weak at this point but I wanted to prove that my chin was solid," he added after Mormeck had threatened to "smash" the Ukrainian's "glass-jaw" in the pre-fight build up.

"From the first round, I set the pace and I controlled the fight the whole time. I expected him to come forward and I also knew he had no chance of succeeding with his plan. He insisted on it, however, and the end was inevitable." Mormeck, who turns 40 in June, was put on the canvas as early as the second round and despite rallying in the third, Klitschko finished the fight with a combination mid-way through the fourth before the referee stepped in.

"I think Jean-Marc was surprised by the strength, speed and balance of my boxing right off the bat," said Klitschko. "I think he didn't expect it and it was difficult for him to restart after the first shot that I landed on him in the second round."

Mormeck barely landed a decent shot all night and Klitschko's one-sided victory did little to improve the image of the sport that was tarnished by last month's press conference brawl between Haye and Dereck Chisora. "This was an execution without sporting value," said former European champion Luan Krasniqi after the fight.

With no serious heavyweight contenders in the United States, it remains to be seen who can challenge the Klitschkos domination of the division, with Wladimir's elder brother Vitali holding the WBC belt. Russia's Alexander Povetkin was disappointing in his recent points win over Marco Huck and in July Wladimir has a mandatory defence of his IBF title against 40-year-old American Tony Thompson, who he already knocked out in 2008.