Former champions Williams have become the first current Formula One team to sign up for the 2010 championship despite an ongoing standoff over the regulations that has left Ferrari threatening to quit.
Responding to a tipoff to Reuters from another source, Williams chief executive Adam Parr confirmed the entry on Monday but stressed the team remained committed to the Formula One Teams Association (FOTA).
"The unity of FOTA is of paramount importance to Williams," he told Reuters.
"Yesterday we joined the other members of FOTA in writing to the FIA (International Automobile Federation) to request a continuing effort to find a compromise concerning the regulations for 2010."
Parr said Williams and FOTA were also seeking an early signing of a new Concorde Agreement, the confidential accord governing the sport which the teams, FIA and commercial supremo Bernie Ecclestone have yet to put their names to.
"We believe that under the leadership of (Ferrari president Luca) di Montezemolo and (Toyota motorsport president) John Howett, FOTA has extracted some very significant concessions from the FIA," said Parr.
"These include not only the procedural aspects of the budget cap but also other elements that will enable the higher budget teams to participate.
"Having said that, Williams has -- and has always maintained -- that we have a binding contract with both FOM (Ecclestone's Formula One Management) and the FIA to participate in the world championship from 2008 to 2010.
"We have been paid in full for our participation and we feel both morally and legally obliged to make it clear that we will participate in Formula One in the future as we have in the past 30 years.
"We owe this to our employees, our sponsors and the fans, all of whom are affected by statements that the teams may not enter next year's championship."
FERRARI THREAT
Champions Ferrari have threatened to quit the sport after an unbroken 60 years of competition if the 2010 rules are not re-written.
So too have former champions Renault, Toyota and the two Red Bull-owned teams, half of the current teams on the grid.
The main stumbling block concerns an optional 40 million pounds ($63.74 million) budget cap that the the FIA wants to introduce to cut costs and help new teams enter.
Those accepting the budget cap would be given greater technical freedom, something Ferrari say would create an unacceptable two-tier series.
FIA president Max Mosley suggested on Sunday that the cap could be delayed a year and has said he expects all teams to compete under the same rules.
Williams, the second most successful Formula One team after Ferrari in terms of constructors' titles, have Toyota engines but are an independent team.
They had been expected to sign up because, unlike the car manufacturers that dominate the sport, Formula One is their sole focus and they could not afford to risk being left out with at least 10 new teams also seeking to come in.
"We will continue to work within FOTA and with FOM and FIA to find a compromise but no-one should be in any doubt about our commitment to the FIA F1 world championship," said Parr.
An FIA spokesman said the governing body would publish the 2010 entry list in June.