West Ham face a challenge to convince Filip Kostic to move to the club this summer.
Jacob Steinberg of The Guardian reports that the Hammers are attempting to do a deal for the wing-back this summer. 
We confirmed over the weekend that there is interest from the Irons in signing the Eintracht Frankfurt star but there are complications in the pursuit.
Frankfurt won the Europa League last season, knocking the Irons out en route to the final, and have subsequently qualified for the Champions League.
As a result, the Hammers will need to convince Kostic to give that up if he is to move to east London; talks between the two clubs are said to be ongoing, however.
By comparison, West Ham are likely to sign Gianluca Scamacca from Sassuolo, with personal terms now having been agreed, again per Steinberg.
David Moyes is desperate to continue reinforcing his squad after signing Nayef Aguerd, Flynn Downes, and Alphonse Areola.
Scamacca brilliant business , Kosticcwould be amazing . However Onana looks like the real deal if we get all 3 and a left back we will be strong . COYI ⚒
Agree, it would be a good bit of business.
I would like a younger LW, maybe like Kliuvert who is still an option. We do have an old squad