Renault joined Ferrari in threatening to withdraw from next season's Formula One world championship because of the budget cap imposed by the sport's governing body.

Renault said Wednesday it is frustrated that FIA adopted the new regulations while ignoring alternative plans proposed by the teams.

Like Ferrari a day earlier, Renault said it will only take part in the 2010 championship if FIA revokes the new regulations _ putting pressure on the ruling body ahead of a meeting between all parties at a Heathrow airport hotel on Friday.

FIA president Max Mosley is leading the FIA's push to curb costs, with a voluntary $60-million budget cap being made available to teams. Teams that don't adhere to the cap will not receive the same technical freedom.

Big teams fear the rules will effectively split F1 into two tiers, those that can live with the cap and enjoy the technical advantages and those that can't.

Ferrari won the constructors' championship eight of the last 10 seasons, with Renault winning the other two.

"Renault has always considered Formula One as the pinnacle of motor sport and the perfect stage to demonstrate technical excellence," Renault F1 team president Bernard Rey said in a statement. "We remain committed to the sport.

"However, we cannot be involved in a championship operating with different sets of rules and, if such rules are put into effect, we will be forced to pull out at the end of this season."

Under Mosley's plan, teams can opt out of the budget cap but must adhere to the current regulations. Those teams agreeing to the cap will be allowed a more powerful engine and aerodynamic aids, both of which should considerably boost performance.

"The idea of having a championship with two velocities _ with cars, which for example are allowed to have flexible wings or an engine without a rev limiter _ is absurd," Ferrari driver Felipe Massa said.

Massa's teammate, Kimi Raikkonen, agreed.

"I can't imagine drivers racing each other on the track with cars built according to different rules," Raikkonen said. "That wouldn't be good for the sport itself or for the fans. If that should happen, it would be too bad and I understand that a company like Ferrari is thinking about racing somewhere else."

It is likely that the threats are designed to strengthen the teams' hands ahead of Friday's meeting, when they can restate their demands for gradually introduced cost-cutting.

"Our aim is to reduce costs while maintaining the high standards that make Formula One one of the most prestigious brands on the market," Renault F1 team managing director Flavio Briatore said. "We want to achieve this in a coordinated manner with the regulatory and commercial bodies, and we refuse to accept unilateral governance handed out by the FIA."

Renault, which won the constructors' championship in 2005 and 2006, is second to Brawn after five races this season. Ferrari is a distant seventh.