Athletic Bilbao have reportedly increased the release clause in Aymeric Laporte's contract.
The French centre-back is widely regarded as one of the best young talents in European football, with Barcelona credited with a strong interest in his services.
Laporte's release clause had stood at £30m, but according to AS, the release figure is now £34m.
The 20-year-old revealed last week that he was flattered by talk of a move to Barcelona, but also insisted that he was "happy at Bilbao".
Laporte has been with Bilbao since 2010.
