Maskaev (34-5, 26 KOs) won the WBC heavyweight title by knocking out Hasim Rahman in August 2006, but the Russian-American champion hasn't been back in the ring since December because of injuries and slow negotiations for new fights.
Last Friday, he scrapped his scheduled bout with Peter at Madison Square Garden because of several herniated discs in his back. Maskaev is expected to be out of action for at least three more months.
Faced with more than 14 months without a heavyweight title fight, the WBC's board of governors voted to hand the interim title to Peter (28-1, 22 KOs), the rising Nigerian fighter.
He still hopes to appear at the Garden on Oct. 6, though a replacement opponent hasn't been chosen or approved. Andrew Golota, the erratic Polish heavyweight who's winless in four previous title bouts, is thought to be the leading candidate.
Peter hasn't lost in four fights since dropping a decision to Vladimir Klitschko in September 2005 despite knocking down the current IBF champion three times. Peter beat James Toney twice in WBC elimination bouts over the last year while waiting for a title shot.
Peter's fight with Maskaev was to be the centerpiece of the first fight card on the Garden's new ring after its 82-year-old ring was donated to the International Boxing Hall of Fame.