Sky Sports News understands Birmingham have joined West Ham in the race to sign Juan Roman Riquelme.
The 32-year-old midfielder is currently out of contract after spending the last three years with Boca Juniors, and Blues are keen to bring him to the Premier League.
Blues' bid for Riquelme, who has also attracted interest from Brazilian club Flamengo this summer, could be hindered by the fact that Boca are looking to re-sign the talented playmaker.
And Riquelme revealed last week he would prefer to stay on at the Buenos Aires-based club, where he began his professional career back in 1996.
West Ham's efforts to sign Riquelme have also stalled as they are yet to match the personal terms being demanded by the player.