WBO, IBF and WBA heavyweight champion Wladimir Klitschko pulled out of his fight against French challenger Jean-Marc Mormeck on Monday after undergoing an operation to remove a kidney stone.
The fight had been scheduled for Saturday in Duesseldorf.
Klitschko's promoter, Bernd Boente, said on Monday that 3 March was a possible new date for the fight. The IBF would have to approve it because nominally Klitschko would be requested to fight a mandatory challenger on that date.
"We hope to know in two or three days. Mormeck is also ready to accept it," Boente said.
Klitschko had abdominal pain at his training camp in Austria on Friday. The 35-year-old Ukrainian was taken to Innsbruck for initial treatment before being transferred to a Duesseldorf hospital. The stone was removed Saturday but Klitschko returned to the hospital Sunday before a scheduled television appearance.
His older brother Vitali, the WBC champion, appeared on the live program and said Wladimir was taken ill shortly before the show and returned to the Duesseldorf hospital.
He declined to give any details.
The 39-year-old Mormeck is a former WBC and WBA unified cruiserweight champion. He has won all his fights since moving to the heavyweight division in 2009. He has a career record of 36 wins (22 KOs) and four defeats.
Saturday's fight was supposed to be Klitschko's 20th title bout and his first appearance since beating British boxer David Haye in July. His record is 56-3 with 49 KOs.