Mosley is refusing to give ground to the teams' demands
The head of world motorsport Max Mosley has warned the Formula 1 Teams' Association (Fota) there is no time to spare in the on-going budget row.
World governing body the FIA has given Fota members until 19 June to accept new rules and a budget cap or risk exclusion from the 2010 season.
On Wednesday Fota wrote to Mosley suggesting an extension for more talks.
But he insists Friday remains the cut-off date for teams like McLaren and Ferrari who have yet to sign up.
Mosley has offered some concessions to the teams, however, saying that if they accept the 2010 rule changes as published, the new measures could be revised "in due course."
Autosport magazine reports that Mosley has told teams that he is prepared to discuss the FIA's International Court of Appeal, and also remove the controversial appendix five to the 2010 Sporting Regulations.
This has been a particularly thorny issue for teams, who are concerned it would give the FIA a free hand to impose whatever rules they wanted.
Now is the time to find a reasonable and rapid solution to the outstanding issues
Latest Fota letter to the FIA
In addition, he is also thought to be willing to change some of the technical regulations for next year.
If the teams agree, rules on moveable wings will remain as they are this year, four wheel drive cars will not be allowed, tyre warmers will still be allowed and rules relating to engines, gearboxes and testing limitations will stay as they are at the moment.
Of the teams on the 2009 F1 grid, so far only Williams and Force India have definitely signed up for next year, as a result of which they were suspended from Fota.
Earlier this month, all 10 current F1 teams were included on the list of entrants for next season, although five of them - Brawn GP, McLaren, Renault, Toyota and BMW Sauber - were only provisional entries, and Ferrari insisted they would not enter under the proposed rules.
Three new teams - Campos Grand Prix, Manor and US F1 - have also signed up.
If the two sides are unable to reach an agreement by the deadline, the FIA has confirmed more new entrants will be named to make up the 13-team, 26-car grid.
They would essentially replace some of the biggest names in the sport's history - a prospect that does not appeal to some of the current leading drivers, who have already spoken in favour of potentially taking part in a breakaway rival championship.
The Fota letter, sent on Wednesday, is addressed to FIA president Mosley - the driving force behind a £40m per team per season budget cap - and F1's commercial supremo Bernie Ecclestone.
"We hope that you will consider that this letter represents significant movement by the teams, all of whom have clearly stated a willingness to commit to the sport until the end of 2012," it said.
"We would therefore strongly but respectfully submit that you consider these proposals and seek to avoid the potential departure from F1 of some important teams.
"Now is the time to find a reasonable and rapid solution to the outstanding issues."
The FIA wants to introduce budgetary restrictions to "ensure that F1 is the most technologically challenging motorsport".
It has accused Fota members of wanting to take over the running of the sport.
"The FIA and FOM (Formula One Management) have together spent decades building the FIA Formula 1 World Championship into the most watched motorsport competition in history," said the FIA.
"In light of the success of the FIA's Championship, Fota - made up of participants who come and go as it suits them - has set itself two clear objectives: to take over the regulation of F1 from the FIA, and to expropriate the commercial rights for itself.
"These are not objectives which the FIA can accept."
The teams have expressed concern that the way the rules would be enforced would be intrusive on the running of their business, but the FIA rejects this suggestion.
"If there is no intention to cheat, regulation should not present a threat," it said.
"The FIA already regulates every aspect of technical performance and deals with vast amounts of confidential proprietary technical information without partiality or 'interference'.
"For several of the existing teams, the idea of greater technical freedom with financial constraints was very attractive.
"Left to their own devices, at least half the existing teams would have adopted those rules."