The winger has not featured in the club's recent games as he pushes for an exit from the City Ground.
The Mail reported yesterday that Forest had accepted a £7 million offer from West Ham for Antonio, yet there appears to be a hitch over the potential transfer.
SkySports report: "Sources close to the player are not confident a deal can be struck in time to beat the 6pm deadline."
Antonio joined Forest for just £1.5 million from Sheffield Wednesday a year ago, and finished the season as the club's joint top scorer in all competitions last season.
Forest have been resistant to approaches from fellow Championship sides over his services, but Antonio was recently dropped from the team by manager Dougie Freedman due to a lack of focus.
Keeping him would be a big win for the club, as well as a disappointment for West Ham. The Hammers do have other options however, with SkySports reporting Victor Moses will sign on a season long loan from Chelsea.