West Ham chiefs want a deal worth £20million in total for Grady Diangana after West Brom tabled an initial £12m bid, Football Insider understands.
A West Ham source has told Football Insider that the hierarchy want a fee of up to £20m including add-ons as well as a release clause inserted into any transfer package.
They have made clear their stance to the newly-promoted Baggies, who have been encouraged to make a formal move for Diangana as the possibility of a big-money deal increases.
The winger wants to be playing regular first-team football next season and is willing to leave West Ham to get that.
The possibility of the Irons academy product leaving London Stadium will further anger fans already frustrated at a lack of summer activity.
The wide man was a big success at West Brom in their successful Championship promotion campaign last season, contributing eight goals and seven assists in 31 appearances in all competitons.
Operating mainly on the left flank, he also has 21 first-team appearances for West Ham under his belt.
The decision to sell Diangana would be hugely unpopular with supporters at the London Stadium who love to see homegrown talent break through the youth ranks and into the senior side.
The young winger has the likes of Andriy Yarmolenko, Felipe Anderson, Manuel Lanzini, Robert Snodgrass and Pablo Fornals for competition in attack.
In other West Ham news, Frank McAvennie claims the club will sell £80million-rated player in a massive part-exchange deal.