Red Bull have joined champions Ferrari [Images] in agreeing to extend Formula One's existing commercial agreement to 2012 and turning their backs on a rival series.

"Red Bull Racing confirms that it has reached an understanding with FOA (Formula One Administration) to prolong the current Concorde Agreement from 2008 until 2012," the team announced on its website.

The decision ends Ferrari's political isolation in the Grand Prix paddock where the other eight teams are still considering the carmakers' vision of a separate race calendar.

It came as no surprise, however, as Red Bull are contracted to use Ferrari engines from next season.

The Concorde Agreement between the teams, the governing International Automobile Federation (FIA) and commercial supremo Bernie Ecclestone's FOA expires at the end of 2007.

Team boss Christian Horner said Red Bull, owned by Austrian energy drink billionaire Dietrich Mateschitz, had simply acted as they saw fit.

"This was a totally independent decision," he told Reuters.

"We felt the timing was right to state our intentions. Hopefully all the parties will get around the table in the near future but we wanted to make a decision prior to being involved in a meeting that involved voting."

POWER STRUGGLE

The carmakers -- a core of Renault, BMW [Images] and Mercedes with Toyota and Honda backing them but not yet formally aligned -- are due to get together with the teams at Hockenheim during this weekend's German Grand Prix.

They are expected to finalise their own proposals for rule changes and how the sport should be run from 2008, with an emphasis on transparency and teams competing on equal terms.

A spokesman for the manufacturers, formerly grouped under the GPWC banner, said the group's strategy would not change as a result of the Red Bull decision.

There was no immediate comment from the FIA or Ecclestone on Red Bull's position.

The sport is caught in a power struggle and the FIA, Ecclestone and Ferrari have been on one side with the manufacturers on the other in a battle for control of revenues and governance.

Some see the threatened rival series as more of a bargaining ploy than serious intent, with the carmakers seeking the bulk of the revenues to make their teams self-financing.

FIAT-owned Ferrari, the sport's glamour team and the only ones to have been in Formula One since the first championship in 1950, agreed to extend the agreement in January in a surprise break with the other carmakers.

Since then the other teams have kept Ferrari isolated by not attending meetings with the FIA to discuss rule changes.

Renault and Toyota own their own teams and BMW are buying Sauber, whose deal to use Ferrari engines ends this season. Honda own 45 percent of BAR while Mercedes' parent DaimlerChrysler owns 40 percent of McLaren.

Williams are partnered by BMW at present while Minardi are powered by privately-owned Cosworth.

Jordan, owned by Russian-born Canadian billionaire Alex Shnaider, are currently assessing their options but have Toyota engines this year.

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