Valencia have reportedly told Arsenal that they will not accept a bid of less than £50m for defender Shkodran Mustafi.
The Gunners have been linked with the Germany international in recent weeks as manager Arsene Wenger looks for defensive reinforcements following injuries to Per Mertesacker and Gabriel Paulista.
However, Valencia's initial asking price of £35m was thought to have been more than Arsenal are willing to pay, and The Mirror now reports that the Spanish outfit have increased it further.
Discussions between the two clubs are understood to be ongoing, although Arsenal value the 24-year-old at closer to £25m.
The Gunners have also been linked with Jonny Evans and Jose Gimenez, while Valencia are thought to be willing to sell Mustafi in order to fund a move for Chelsea forward Pedro.