West Ham have made a €30 million bid to Sporting CP for William Carvalho and currently have a delegation in Lisbon trying to complete a deal, Goal understands.
The Hammers look to continue a busy transfer window that has seen them land Javier 'Chicharito' Hernandez, Joe Hart, Marko Arnautovic and Pablo Zabaleta.
The Portuguese club are demanding €40m for Carvalho, but West Ham do not agree to that valuation and are hopeful of reaching a compromise.
The Portugal international midfielder has been linked to Premier League sides Arsenal and Manchester United in the past, but sources tell Goal that West Ham are optimistic a deal will get done.
Carvalho scored two goals and added three assists in Portugal’s top division last season.
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Sporting signed Rodrigo Battaglia earlier this summer - another midfielder - and it's been widely rumoured that he could replace Carvalho.
West Ham open their season on Sunday at Old Trafford against Manchester United.