The Brazilian, Canadian and German Grands Prix are all in doubt for the 2017 Formula 1 season.
Each race was listed as subject to confirmation on the first provisional 2017 calendar published by governing body the FIA on Wednesday.
Brazil is facing financial troubles, Germany's problems come from the financial collapse of the Nurburgring and Canada has to improve its track.
Brazilian organisers said they had a deal to 2020 and the race would happen.
A statement released on Wednesday said: "The Brazilian Grand Prix Organisation took notice, with surprise, of the 2017 F1 calendar which shows the race to be confirmed.
"There is a contract in place until 2020, every provision of which will be complied with as it has been for the past 45 years."
But insiders have said to BBC Sport that F1 commercial boss Bernie Ecclestone told FIA bosses on Wednesday that the race would be dropped unless the organisers in Sao Paulo found a significant amount more money.
At Thursday's Malaysian Grand Prix drivers' news conferences, Brazilian driver Felipe Massa said: "It would be really disappointing to lose the race in Brazil.
"Brazil is part of this sport and been part of Formula 1 for a long time.
"I know the situation in Brazil is not easy economically. Maybe it is just some pressure but maybe it can happen (not go ahead) like what happened in Germany last year.
"Interlagos is one of the most fun and great races to watch."
The German race has a contract to alternate between Hockenheim and the Nurburgring.
But the Nurburgring has not held a grand prix since 2013 as a result of financial difficulties.
Hockenheim refused to host the race in 2015 because it said it could not sustain a grand prix every year on financial grounds.
It has been listed as the host race for next year, when it is again the Nurburgring's turn, but no deal has yet been completed.
The problems for Canada revolve around the organisers' failure to complete renovation works that they promised as part of their latest contract.
The paddock area, which is cramped by modern standards, is scheduled to be updated at the Circuit Gilles Villeneuve in Montreal.
However, it is hard to imagine the race being dropped, especially as new owners Liberty Media have made it clear that one of their priorities is to expand the sport's profile in the Americas.
The calendar closely echoes this year's record 21-race season.
It will start in Australia on 26 March and end in Abu Dhabi on 26 November. The British Grand Prix is on 9 July.
The first four races are shuffled, so China follows a week after Australia, replacing Bahrain as the second race.
Malaysia is moved to 17 September and becomes the first of the long-haul 'fly-away' races that bring the season to a close, a position previously held by Singapore.
The full provisional calendar is as follows:
26 March: Australia
9 April: China
16 April: Bahrain
30 April: Russia
14 May: Spain
28 May: Monaco
11 June: Canada *
18 June: Azerbaijan
2 July: Austria
9 July: Britain
23 July: Hungary
30 July: Germany *
27 August: Belgium
3 September: Italy
17 September: Malaysia
1 October: Singapore
8 October: Japan
22 October: USA
5 November: Mexico City
12 November: Brazil*
26 November: Abu Dhabi