Vitali Klitschko's manager Berndt Boente has given David Haye a five-week deadline to decide if he wants to fight the WBC heavyweight champion.
The Ukrainian faces Dereck Chisora at the Olympiahalle in Munich on February 18, with talks of a possible bout with Haye apparently stalling.
Klitschko's camp have said that the former WBA champion has made "unrealistic" financial demands.
"We do not know who Vitali's opponent is going to be [beyond Chisora]," Boente told boxingscene.com.
"We were negotiating with Haye, but most likely the fight will never happen.
"Haye has four, five weeks to give us a definitive answer, otherwise we will start negotiations with other boxers."
Haye, 31, announced his retirement in October following his defeat to Vitali's younger brother, Wladimir, in July.
