Led by car-makers Renault, BMW, Honda, Daimler-Chrysler and Toyota, the Grand Prix Manufacturers' Association (GMPA) is demanding a greater share of F1 income.
The GPMA has been involved in "constructive" talks with motorsport's governing body, the FIA, over the summer, reports the BBC.
However, the GPMA said it is ready to start work on carrying out its threat of the breakaway series when F1's ruling Concorde Agreement expires in 2008.






