West Ham United have made a £20m offer to sign Sporting Lisbon midfielder Bruno Fernandes, according to Sky sources.
Sporting, who face losing a number of key players after they asked to have their contracts terminated, are, however, looking for a fee of £25m.
One other Premier League club has shown concrete interest in Fernandes and it is thought La Liga giants Atletico Madrid are also keen on him.
The 23-year-old starred for Portugal at the World Cup before they were knocked out in the last 16 by Uruguay, and he is among the Sporting players to have requested for their contracts to be terminated, citing "just cause".
Fernandes, Gelson Martins and several others made the move following an attack on players and staff by a group of around 50 people at their training ground in May.
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Fernandes could, therefore, have been available for free but a compromise is being worked on whereby the club would receive a cut-price transfer fee.
Fernandes came through the Sporting academy and has made 45 first-team appearances, scoring 15 goals. He has also spent time on loan at Italian clubs Sampdoria and Udinese.
West Ham have signed three players for new manager Manuel Pellegrini so far in the summer transfer, including French defender Issa Diop, Swansea 'keeper Lukasz Fabianski and Fulham right-back Ryan Fredericks.
The Hammers have also made a bid for Nice striker Alessane Plea and Lazio's Felipe Anderson, while showing interest in free agent Jack Wilshere, Roberto Inglese, Jean Michael Seri, Armando Izzo, Alfie Mawson and Barcelona's Marlon Santos.