Bernie Ecclestone's plans for the future of Formula One received a major boost on Wednesday when former world champions Williams confirmed their support.
Williams join Ferrari, Midland/Jordan, Red Bull and Toro Rosso/Minardi in agreeing an extension with Ecclestone when his Concorde Agreement with the teams expires at the end of 2007.
Five carmakers -- Daimler-Chrysler's Mercedes, Renault, BMW, Honda and Toyota -- are at odds with Ecclestone over the sport's commercial arrangements and have threatened to set up a rival series to Formula One in 2008.
Williams had been undecided but said on Wednesday it wanted to remove "the damaging uncertainty hanging over our sport".
"WilliamsF1 has agreed to become a signatory to the new Concorde Agreement after confirming that the commercial rights holder ... had agreed to an improved distribution of commercial revenues among participating teams," a Williams statement said.
"The agreement commits one of the most successful names in the sport's history to Formula One after 2008, and is an important step towards protecting against a divisive split that could undermine motor racing's premier series."
Williams had a poor 2005, finishing fifth in the constructors' championship, and their engine partner BMW and main sponsor Hewlett-Packard have now left. They will have to pay for their Cosworth engines next season.
DaimlerChrysler holds a 40 percent stake in McLaren, now the only one of the sport's big three teams to stand firm against Ecclestone whose new agreement extends to the end of 2012.
The Briton has linked with CVC Capital Partners to retain control of Formula One after the sport's biggest shareholder, German bank BayernLB, sold its stake to CVC last month.
The five carmakers, grouped as the Grand Prix Manufacturers Association (GPMA), want more transparency in the sport and a bigger slice of the commercial earnings.
In a statement after Williams' announcement, the GPMA said the five "reaffirmed their binding agreement to race together only in a series which satisfies the fundamental principles of a clear and equitable World Championship".
"While the GPMA members and their affiliated teams appreciate that progress has been made in recent negotiations, they remain committed to their objective to further develop the sport for the benefit of all stakeholders and in particular the fans."
