Formula One's ruling body has indicated that the Williams and McLaren teams will have to use new Michelin tyres for Sunday's Italian Grand Prix.
McLaren fear the tyre issue will affect Raikkonen's title chances
The two teams held a meeting with the FIA on Monday in an attempt to find a solution to what they regard as rule changes which could hand the title to Michael Schumacher and Ferrari.
But the FIA has confirmed that it stands by its decision to check the tread of tyres after the race as well as before it, meaning teams would risk punishment if they continue to use the old Michelins.
"A number of press reports have suggested that the FIA has changed or re-interpreted the tyre regulations. This is not correct," the FIA said in a statement.
"The maximum tread width has been 270mm since 1999. The FIA has never suggested that tread width was unlimited once the tyre was in use.
"With hindsight it it regrettable that those using the earlier Michelin front tyres did not consult the FIA about possible excess tread width as soon as they became aware of it.
"However, as far as the FIA technical department is concerned, the matter is now closed and the championship can continue with all teams on an equal footing."
Ferrari have complained that the Michelin tyres used by their rivals are illegal because they have more than the maximum permitted tread.
The Italian team, which uses Bridgestone tyres, has even threatened to challenge every race result this season.
McLaren chairman Ron Dennis and managing director Martin Whitmarsh joined with Frank Williams and his technical director Patrick Head at a meeting with Charlie Whiting, the FIA technical delegate, at McLaren's headquarters on Monday.
Ferrari's rivals fear the FIA's stance will boost Schumacher, who leads Williams driver Juan Pablo Montoya by one point and McLaren's Kimi Raikkonen by two in the drivers' standings.
"Potentially, this whole affair is throwing the world championship out of the window for both of us," Whitmarsh told the Guardian newspaper.
"We talked at length to Charlie but there is still a considerable concern about the issue of approving the tyres' conformity at the end of the race, even though Michelin have produced some new rubber which we tested at Monza last week.
"Put simply, we can either use the existing tyres and risk not conforming with these revised rule interpretations or we can use new tyres and still risk being illegal despite a loss of performance," he said.
"Michelin has done a great job, but the changes in set-up we have had to make - to toe-in, camber and tyre pressures - have not worked to our advantage."