FRANKFURT, Germany — Hasim Rahman has stepped in to challenge Wladimir Klitschko for his IBF heavyweight title.

Promoters said Tuesday that Rahman was selected as the replacement for Alexander Povetkin of Russia, who pulled out of the Dec. 13 fight in Mannheim, Germany, because of an ankle injury.

Rahman, a 35-year-old American, previously held the title in 2001 after knocking out Lennox Lewis. He has a 45-6 record (36 KOs), with two draws.

Klitschko (51-3, 45 KOs), generally considered the world's top heavyweight, stopped Tony Thompson in the 11th round of his last bout on July 12. He has been the IBF champion for 2 1/2 years, and he reclaimed the WBO belt last February with a one-sided decision over Sultan Ibragimov at Madison Square Garden.

Rahman was scheduled to fight Klitschko's older brother, Vitali, in 2005 for the WBC belt, but the fight was postponed twice before Klitschko retired following a string of injuries. Rahman was awarded the title, which he later lost to Oleg Maskaev.

Vitali Klitschko returned from the 46-month layoff to reclaim the WBC heavyweight title on Oct. 11, stopping Samuel Peter after eight rounds. Ruslan Chagaev is the WBA heavyweight champion.