Both Sky Sports and The Birmingham mail are claiming that a deal has been agreed for the out of contract 27-year-old former Real Mallorca and Sevilla winger.
An initial season-long loan deal is said to be the most likely option that Blues will take on Lopez with the option of a permanent three-year contract when the loan deal expires.
Lopez, who has previously had trials at both Blackburn and Portsmouth, played for Blues reserves in a behind-closed-doors friendly against Cheltenham Town on Tuesday.