West Ham have agreed a fee of 40m euros (£33.5m) including add-ons for Lille midfielder Amadou Onana.
However, the deal for Onana, 20, is not completed yet and personal terms are still to be agreed for the player.
The Hammers are also interested in signing Burnley playmaker Maxwel Cornet, 25, who scored nine goals in 26 games for the Clarets last season.
Dakar-born Onana was capped at youth level before making his senior Belgium debut in a 4-1 Nations League defeat to the Netherlands in June.
The 6ft 5in (1.98m) prospect began his youth career at Belgian clubs Anderlecht, RWS Bruxelles and Zulte Waregem before spending three seasons with Hoffenheim's academy.