Haye bowed out of the fight on Wednesday, saying he had injured his back in training, and said he wanted to push the date back to July.

But Klitschko, who holds the IBF and WBO belts, said he was in top form and wanted to keep the date — a 60,000-ticket sellout at Schalke’s soccer stadium in Gelsenkirchen, Germany.

"It’s unfortunate that David Haye can’t compete. But now I’m looking ahead and I’m excited about a particularly sporting challenge with Ruslan Chagaev," Klitschko (52-3) said in a statement released Saturday by his management company, KMG.

Chagaev has been the WBA’s "champion in recess" since withdrawing from two scheduled rematches against Nikolai Valuev. A third match between the two fighters scheduled for last Saturday in Helsinki was canceled after Finnish boxing authorities said Chagaev failed a "medical requirement."

The WBA had said that the two must fight before the end of this month to decide ownership of the title, but has not announced what the most recent cancellation means for that deadline.

Klitschko’s manager, Bernd Boente, said Valuev was also considered as a potential challenger for the 20 June fight.

In February, Chagaev (25-0-1) won a technical decision over Carl Davis Drumond at Rostock, Germany — the Uzbekistan-born boxer’s first fight in more than a year.