Both teams owned by Red Bull have joined Toyota in threatening to pull out of Formula One if the sport's ruling body does not make changes to its controversial budget-cap rules for next year.
The Red Bull Racing and Toro Rosso teams are both operated by Red Bull owner Dietrich Mateschitz, who's told an Austrian newspaper he plans to boycott the planned rule changes.
Toyota said on Sunday they did not support the new rules - which, it is claimed, would create a two-tier championship - and would not lodge an entry bid for 2010 unless they were changed.
Mateschitz hopes there will be a meeting and a settlement before the May 29 entry deadline.
Formula One sources say it looks as if only Brawn GP, Williams and Force India are prepared to to comply with the International Automobile Federation's cost cutting plans.
Teams that comply will be allowed much greater technical freedom and unlimited out-of-season testing. Testing in the season is currently banned.