Athletic Bilbao have rejected Manchester United's offer of 36 million euros ($49 million, £29 million) to buy midfielder Ander Herrera, the Spanish club said on Thursday.

"Athletic Club rejected this week an offer by Manchester United of 36 million euros to transfer the federative and economic rights of the player Ander Herrera," the Basque side said in a statement.

British media reported on Tuesday that a deal could be wrapped within days for the 24-year-old Spaniard, whose fee will reportedly rise at the end of this month due to the terms of his contract.

It would be the English club's first signing since they named Dutchman Louis van Gaal -- currently in charge of the Netherlands team at the World Cup -- in May as the successor to David Moyes.