McLaren team boss Martin Whitmarsh says he would be surprised to see the F1 calendar expand greatly for the 2014 season.
The current campaign is being contest over 19 race after the decision was taken to delay the proposed race in New Jersey, with no replacement found despite a revision being made to the schedule to open up a free date for an additional European event.
The New Jersey race is slated to join the calendar next year after a twelve month delay, while Russia is also set host an F1 event for the first time at the new circuit being build in the city of Sochi.
That would leave a calendar of 21 races if the current 19 races were also run next year, and Whitmarsh said that that number would make things challenging for F1's teams.
"I don't know whether there really will be 21, but I've heard the stories of a variety of new venues, from Russia to talk of New Jersey again," he was quoted by ESPN
. "Well they're both important territories, aren't they, but whether all the other dates on the calendar survive, I don't know. But 21 is a lot of races, that's for sure.
"We've had 19 this year and 20 last year, and I know it's only one more but we've been saying that since we had about 14 races and most of those were in Europe. It gets quite tough for the team."