Formula One's governing body has made teams a final offer in a bid to prevent the sport from tearing itself apart.
Five of the existing teams -- leaders Brawn, BMW-Sauber, McLaren, Renault and Toyota -- risk exclusion if they do not sign up by a tomorrow evening deadline.
Should they fail to do so, there is a risk of teams setting up a rival series with champions Ferrari and the two Red Bull teams also at loggerheads with the International Automobile Federation (FIA).
Both sides are making last-ditch efforts to reach a compromise deal, however.
In a letter to the five provisional teams which was seen by Reuters today, FIA president Max Mosley set out the terms of engagement that effectively set in stone agreements reached before talks broke down this week.
Changes to the published regulations included substituting an optional 40 million pound budget cap with a 100 million euro one for 2010, that figure dropping to 45 million in 2011.
"There will be self-reporting of compliance using a reputable auditor," he added, in a move to overcome the manufacturers' resistance to opening their books to the governing body.
"Any suspicions of breach would be investigated by a mutually acceptable auditor of suitable standing."
Teams indicated on Wednesday that they were prepared to accept such an independent auditor.
Mosley asked the teams to agree in return to be bound by the terms of the 1998 Concorde Agreement that has now expired.
The agreement would then bind them until the end of 2014 or until all teams, the FIA and commercial rights holder signed a new agreement.
"Subject to approval by the FIA's world motor sports council, and by teams already having had their entries...accepted, it is intended that certain amendments...will be made to the 2010 Formula One sporting and technical regulations forthwith," said Mosley.
He added that the amendments were those agreed between the FIA and FOTA at a meeting on June 11.
Mosley added that the FIA was "not averse" to the teams' proposals concerning the International Court of Appeal and was prepared to discuss that and associated changes to the statutes of the governing body.
An appendix to the letter detailed changes to the published regulations, including sticking with the 2009 rules in several areas.
That included engines, although Mosley said the Cosworth unit to be used by at least three new teams would remain unrestricted for 2010 only.
The 2009 rules will continue to apply to gearboxes, testing, tyre warmers and the moveable front wing. Four-wheel drive will not be allowed and the KERS energy recovery system cannot be connected to the front wheels.