Konstantin Osipov said he expected both sides to sign a formal contract within a week.
"The fight will be held on 1 April in Hamburg," he added.
The tallest and heaviest world champion in the history of boxing, Valuev is two metres 13cm (7ft) tall and weighs 147kg (323lb).
He says he hopes to unify the heavyweight title by adding the WBC and IBF belts to his WBA crown.