Jean Todt says one race will definitely fall off the proposed 2012 calendar.
The governing body's World Motor Sport Council last week rubber-stamped a provisional schedule for 2012 featuring an unprecedented 21 race dates.
Among the scheduled events are season opener Bahrain and the inaugural US Grand Prix in Texas, but the only race marked 'subject to confirmation' was Turkey in early May.
It emerged recently that the Istanbul race will not take place next year because officials did not agree to a dramatically increased sanctioning fee demanded by Bernie Ecclestone.
Asked by Spanish newspaper Diario Sport if a record 21 Grands Prix will be held next season, FIA president Todt answered: "Absolutely not.
"There are 21 dates, but the championship will be 20 Grands Prix."
Asked if Turkey's conditional date means Istanbul Park is the one that will be dropped, the Frenchman said: "I don't know which one will go, but the championship will be 20 races."