Bernie Ecclestone has admitted Barcelona might be the first casualty as F1's annual calendar sheds some European races.
The F1 chief executive told Spanish sports newspaper Marca that the continent's dwindling presence on the schedule could drop to as few as just five rounds per season within the next few years.
Currently, there are two races - Valencia and Barcelona - in Spain.
Asked if that is sustainable, Ecclestone answered: "I don't know, we will have to wait and see.
"I think not, but we'll see.
"In Barcelona they complain that it is difficult for them to balance their accounts."
Barcelona's Circuit de Catalunya has hosted the annual Spanish Grand Prix since 1991.
The event has a contract until 2013 and Ecclestone said it will be honoured.
"Yes, we have a contract in force so it depends whether Barcelona want to keep going or not," he said.