Ukrainian Wladimir Klitschko retained his heavyweight world titles on Saturday with a lopsided 12-round unanimous decision over previously unbeaten American Bryant Jennings.

In the bout at the fabled Madison Square Garden in New York City, Klitschko did little to impress US fans who have failed to jump on his bandwagon despite his seemingly impenetrable reign.

Klitschko improved to 65-3 with 54 knockouts, earning his 22nd straight victory and making his 18th straight heavyweight world title defense.

He is approaching the record of 25 title defenses made by American legend Joe Louis in the sport's glamor division.

Klitschko, who put his International Boxing Federation, World Boxing Association and World Boxing Organization (WBO) belts on the line, used his left jab to take charge early.

He used the advantage of his 1.98-meter hight - to Jennings' 1.91 - to good advantage although the challenger, who was working as a janitor in 2004 when Klitschko last lost a fight, gave the champion some trouble with his quick movement and darting advances in the middle rounds.

Klitschko responded in the final round with some heavy blows, and even with the champion docked a point by referee Michael Griffin for repeated holding, the score cards weren't close.

Cheers were ringing and Ukrainian flags waving by the time the scores were announced. Two judges saw it 116-111 for Klitschko, while the third made it 118-109 for the champion.

"I think that the score cards were way off," said Jennings, who fell to 19-1 with 10 knockouts, adding that he believed the fight "probably could have gone either way."

Klitschko acknowledged that Jennings was more competitive than any opponent he had faced in recent years.

"Absolutely," Klitschko said. "Great hand speed, great foot work, very athletic and a great desire to win the fight and be champion.

"Bryant didn't give me a chance to throw the right as much as I wanted," said ­Klitschko, whose 27th appearance in a heavyweight world ­title fight tied Louis for the most in division history.

His next title bout could be for the World Boxing Council crown that once belonged to his brother Vitali, now owned by American Deontay Wilder who beat Canada's Bermane Stiverne for the belt in January.

Klitschko hasn't lost since he was stopped in the fifth round by Lamon Brewster in a WBO title fight on April 10, 2004, in Las Vegas.

Saturday marked his first fight since knocking out previously unbeaten Kubrat Pulev in November, and was his first bout outside Europe since he took the WBO title from Sultan Ibragimov on February 23, 2008.