The Hammers have agreed a deal with Paris Saint-Germain to sign Thilo Kehrer for a fee of 12m.
Kehrer is in London for a medical and personal terms before he leaves for the London Stadium.
The Hammers are hoping to complete the deal in time for him to be available for the game against the Danes.
Kehrer, who is in the last year of his contract, would prefer a move to West Ham.
Four years after joining Paris Saint-Germain, the 20-year-old German has made 128 appearances for the French club, which has won six major domestic trophies.
He was part of the Germany squad that played in the Nations League this summer.
He is mostly a centre-back but can also play as a wing-back or a holdingMidfielder.
While a deal for Kehrer appears to be close to a conclusion, West Ham are also trying to sign a player from another London club.
The clubs are talking about a deal for the left-back, who has two years left on his contract and spent last season on loan at Lyon.
Although Alonso is expected to join Barcelona this month, he is not currently in the running for the left-wing-back position.
West Ham are expected to make an improved offer for Hans Vanaken after Club Brugge rejected their initial offer.
The proposal from the Hammers was thought to be around 10m.
The transfer window will close at 11pm on September 1st.
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