The venue made its formula one debut last year but tickets for the 2009 race are "not selling as fast", promoter Jorge Martinez Aspar, of Valmor Sports, admitted.
Last year we reported that the event sold out after offering 112,771 seats, with Aspar indicating he would consider increasing the capacity of the grandstands for subsequent events.
But he is now telling the Spanish news agency EFE that approximately 35,000 fewer seats will be available for the August 23 race "although we are still investigating".
Aspar added that the reduction in demand was anticipated after seeing significantly fewer tickets sold for the Spanish grand prix in Barcelona in May.
He also laments the FIA-FOTA war, criticizing those who "spoke too much". "My hope is that from now on the last months can be forgotten," Aspar added.