The Hammers are looking to add to their midfield options this season and have landed on Kostic as suitable target.
Kostic has just a year remaining on his contract with the German side and is able to sign a pre-contract agreement in four months’ time, a possibility that could influence his decision this summer.
West Ham had made an offer near £13m for Kostic but it was turned down by the German club, who want more.
The Hammers are persevering in their hunt for the midfielder and continue to work on getting the deal done.
Eintracht Frankfurt are looking for £16m for the midfielder and it remains to be seen if West Ham raise their offer to that figure.
West Ham also have to come to an personal agreement with Kostic and talks are going regarding it; the Hammers will be hoping it can be fleshed out.
The Hammers are also working on brigning in another midfield addition in Napoli star Piotr Zielinski, for whom they have offered improved terms after a rejected first bid.
