Formula One's road-car makers say talks aimed at ending the threat of a rival series have made significant progress.
They are due to meet F1 supremo Bernie Ecclestone before Sunday's first race in Bahrain, but are playing down speculation of an imminent deal.
Renault, Honda, Toyota, BMW and Mercedes (McLaren) have threatened to set up a rival series after 2007.
They want a bigger share of revenues, more say in F1's future and are upset at plans to limit technology from '08.
A spokesman for the Grand Prix Manufacturers' Association (GPMA), which comprises the five rebel car makers, said it was hopeful a compromise could be reached.
"We will of course meet with the commercial rights holder this weekend," he said.
"Significant progress has been made and we hope to address several of the outstanding issues.
"But it's too early to predict any outcome. We don't want to speculate but things are moving in the right direction."
Mr Ecclestone, 75, told the Daily Express last week that he was hopeful of getting a deal before the race in Bahrain.
"We can all see the benefits of cutting costs while continuing to allow some areas of research and development and I think there is a mood of conciliation now," he added.
"They will certainly earn a lot more money on the commercial side, double what they got before."
Ecclestone has agreed terms for the 2008 season with six F1 teams including former champions Ferrari and Williams.
But the GPMA, led by BMW board member Burkhard Goeschel, says it will launch its own championship in 2008, if its demands are not met.