Max Mosley has made what appeared to be crucial concessions in the budget cap row that threatens to split Formula One.

As the clock counts down to tomorrow night's deadline when teams have to agree on rules for entering next year, Mosley moved to ease concerns over the cap and the governance of the sport with what has been described as a "final offer".

It is understood that a final round of talks between FIA president Mosley and members of the Formula One Teams' Association, who have threatened to run their own breakaway series in 2010, may now take place at Silverstone ahead of this weekend's British Grand Prix.

Five of the existing 10 teams -championship leaders Brawn, BMW-Sauber, McLaren, Renault and Toyota - risk exclusion if they do not sign up by the FIA's deadline tomorrow.

Three other teams - Ferrari, Red Bull and Toro Rosso - are also siding with the 'renegade five' although the FIA claim they are committed to competing by legally binding contracts.

In his latest letter to FOTA, Mosley set out what the FIA are willing to concede in return for unconditional entries. Changes included substituting an optional £40million budget cap with one for £86m for 2010, that figure dropping to £38m the following years.

FOTA sources suggest they will still seek a considerable increase on the cap for 2011.

"There will be self-reporting of compliance using a reputable auditor," Mosley added, in a move to overcome the manufacturers' resistance to opening their books to the FIA. "Any suspicions of breach would be investigated by a mutually acceptable auditor of suitable standing."

Teams indicated yesterday that they were prepared to accept such an independent auditor. Mosley asked them to agree in return to be bound by the terms of the 1998 Concorde Agreement that has now expired.

The agreement would run until the end of 2014 or by the signing of a new one by all parties.

Mosley added that the FIA were "not averse" to the teams' proposals concerning the International Court of Appeal and were prepared to discuss that and other changes to the statutes of the governing body.

An appendix to Mosley's letter detailed changes to the published regulations, with a return to the 2009 rules governing gearboxes and testing, with tyre warmers and the moveable front wing being retained. Four-wheel drive will not be allowed.

So far, only former champions Williams and Force India of the current teams have signed up unconditionally for 2010. Three new teams have also entered.

Former triple world champion Niki Lauda is dismayed by the infighting which has blighted Formula One this season.

The Austrian said: "Everyone is worried most about losing face and because of that everything could fail.

"That would be the biggest joke of all. I have never experienced anything like this."