Anthony Joshua and Alexander Povetkin have agreed to an anti-doping program as their camps move closer to finalising a deal for a heavyweight world title fight.

The Voluntary Anti-Doping Association welcomed both fighters to its program Sunday ahead of their likely bout in September.

Povetkin, 38, failed two drug tests in 2016 but has signed up to the VADA deal ahead of the proposed clash for the WBA title.

Earlier this week Joshua's promoter Eddie Hearn told ESPN a fight with American WBC heavyweight champion Deontay Wilder had been put on hold after the camps had failed to reach an agreement.

Joshua was told by the World Boxing Association last Tuesday he had to agree terms with Povetkin for a mandatory defence of their title or risk losing his belt.

The champion -- who also holds the IBF and WBO belts -- has held the WBA title since defeating Wladimir Klitschko in 2017.