West Ham boss David Moyes and new sporting director Tim Steidten are at loggerheads over transfer policy.
The Daily Mail says the situation has deteriorated to the point where Moyes could be pushed out before the market shuts.
Moyes has been insisting West Ham focus on signings with Premier League experience, while Steidten is insisting on targeting talent from abroad.
With tensions rising, the board have drawn up a shortlist of potential managerial replacements.
Moyes led West Ham to the Europa Conference League final victory in Prague at the end of last season.