Sporting Lisbon have reportedly rejected a £24m offer from Arsenal for William Carvalho.
The Portuguese international, who represented his country at this summer's World Cup, is widely regarded as one of the best up-and-coming talents in European football.
Manchester United have been strongly linked with a move this summer, but have thus far baulked at the asking price of £36m.
According to The Metro, Sporting are not prepared to sanction a move unless Carvalho's full release clause is paid, meaning that Arsenal need to find another £12m on top of their original offer.
The 22-year-old has been with Sporting since 2005.
