Chase Carey says two current races will not appear on the 2020 calendar.
The F1 CEO has confirmed deals with two new hosts: Vietnam and Zandvoort. But Carey says he does not want to expand the schedule beyond 21 races.
"I think it's important to have something new in our calendar, but we do not want to mess things up every year," he told La Presse.
"We are proud to have lasting relationships with many promoters and the goal is to build long-term partnerships.
"As for the number of grands prix, we will take our time before increasing that. If we have two new events next season, the number of the events will remain stable."
Of the races on the 2019 calendar, there is doubt about the future of several, including Barcelona, Silverstone, Hockenheim, Monza and Mexico.
Also up in the air are new agreements with the teams beyond the 2020 season, including the technical and sporting regulations for 2021.
"We are making progress in the negotiations," Carey reports.
"It is still only for 2021 and so there is no immediate urgency to reach an agreement.
"I think we have laid the groundwork for what we were looking for, and there are already a number of things that have been settled, with the technical regulations in particular," he said.
"That said, there are still major disagreements between the teams. There are ten teams and each one has a different position to the others.
"It's impossible to make all of them happy and it's even likely that they will all be more or less unhappy at the end of the process. The idea is to find the best compromise," Carey added.
