Formula One teams and the governing body remained locked in combat on Friday after the publication of a controversial 2010 entry list that included all 10 current teams as well as newcomers from America and Spain.
While stepping back from the brink, the International Automobile Federation (FIA) made clear in a statement that a long-running standoff that has threatened to tear the sport apart over next year's rules was far from over.
It said that championship leaders Brawn GP, BMW-Sauber, world champion Lewis Hamilton's McLaren team, Renault and Toyota were only provisional entries and could still be shut out if agreement was not reached by next Friday.
They were "invited to lift their conditions" after further discussions, with other would-be entrants waiting to step in should there be no agreement.
Spain's Campos Grand Prix, the American-based U.S. F1 and Britain's Manor Grand Prix were the confirmed newcomers with due diligence still being carried out on others who missed out.
"Our ambition is to first of all prove that we can design and build a car in the United States, as distinct from Europe which is the normal place, and be competing as an American team," said U.S. F1 director Peter Windsor.
"Like everybody else, we hope that it will be one championship."
Those not selected included Kuwaiti-backed Prodrive, former competitors Lola and others seeking to revive the renowned Brabham and Lotus names.
Former champions Williams and tail-enders Force India, suspended from the teams' association FOTA for breaking ranks, are the only current teams to have entered unconditionally.
Champions Ferrari and both Red Bull teams were also deemed to be full entries by the FIA in a controversial step after days of feverish speculation about who would be on the list and whether the existing teams might break away.
The three are all members of FOTA, who submitted a joint entry conditional on the 2010 rules being rewritten and a new commercial agreement signed by Friday.
Ferrari, who had warned the FIA not to include them as an automatic entry and have said they could walk away, reiterated their position in forceful terms after the announcement:
"For the avoidance of any doubt, Ferrari reaffirms that it shall not take part in the 2010 Formula One world championship under the regulations adopted by the FIA in violation of Ferrari's rights under a written agreement with the FIA," the Italian team said.
Red Bull said in a separate statement that its entry was submitted as a conditional one and both its teams were committed to FOTA.
FOTA meanwhile drafted a letter to the FIA's senate and world motor sport council seeking to bypass FIA president Max Mosley in attempts to find a solution.
"We respectfully seek the intervention of the World Council to facilitate solutions to the present situation," the letter said.
"We have attended numerous meetings with the FIA's representatives and have been unable to make any substantive progress."
The FIA, who want to bring in an optional 40 million pound budget cap, maintains that Ferrari and the two Red Bull teams have an existing contract obliging them to compete until 2012.
Ferrari have threatened to end 60 years of unbroken involvement in the sport and walk away if their conditions are not met, with president Luca di Montezemolo saying the budget cap would create an unacceptable two-tier series.
Mosley has remained adamant that a budget cap must be introduced to allow new teams in and protect the sport from the effects of the credit crunch.