Sporting Lisbon have demanded that West Ham United match William Carvalho's buyout clause fee if they want to sign the midfielder, according to reports.
The 25-year-old, who was part of the Portugal squad that won Euro 2016, is a product of the Sporting academy and has scored nine goals in 137 appearances since making his first-team debut in 2011.
Sporting and West Ham are believed to have been in talks over the last fortnight regarding Carvalho's future, with the Hammers reportedly tabling a £25m offer.
However, Sky Sports News claims that the Portuguese giants have opted to play hardball and will only sanction the move if the Hammers trigger the player's £40m clause.
West Ham manager Slaven Bilic has made five major signings during the summer transfer window, with Pablo Zabaleta, Joe Hart, Marko Arnautovic, Javier Hernandez and Sead Haksabanovic arriving at the London Stadium.
