Arsenal are nearing an agreement to sign striker Viktor Gyokeres, 27, from Sporting.
The north London club are expected to pay €63m guaranteed over instalments, with another €10m subject to add-ons.
Sporting reduced their initial demand for a guaranteed €70m over changes of terms on issues like the payment of agent commissions
Manager Mikel Arteta aims to complete the transfer by Thursday
This signing concludes Arsenal's 18-month search for a forward, after previously being deterred by Leipzig's high asking price for Benjamin Sesko.