VIENNA, May 10, 2009 (AFP) - Red Bull on Sunday said they could pull out of the Formula One world championship at the end of the season as the revolt over a proposed budget cap grows even more militant.

Dietrich Mateschitz, the owner of the drinks company which backs the team, wants the FIA, the governing body, to change its rules which would place a ceiling of 45 million euros (S$88.5 million) on each team in a drive to slash the sport's huge costs.

"If the proposed rules for 2010 stay unchanged, we will not take part in the 2010 championship," Mateschitz told the Salzburger Nachrichten newspaper in an interview to be published on Monday.

"Teams of manufacturers will no longer take part. Of the teams now, only two or three will remain," added the Red Bull chief who also runs sister team Toro Rosso.

Under the proposed voluntary budget cap, those teams who spend below the figure will be able to take advantage of various technical benefits which are currently banned under current specifications.

On Saturday, Japanese team Toyota said they too would consider their future in the sport with many teams unhappy with the two-tier budget cap system in 2010.

Toyota president John Howett told www.    autosport.com his team was currently not in a position to commit for next year.

"Under the rules as they are published, we cannot submit an entry," he said.

When asked to clarify what the chances were of Toyota lodging an entry for 2010 by the end of this month, Howett said: "I would say it is very likely we won't enter unless something changes significantly."

On Thursday, Williams technical chief Patrick Head expressed his fears over the risk of a "two-tier championship".