McLaren could meet FIA’s May 29 deadline
Other outfits, including Ferrari, Renault, Toyota and Red Bull, have made clear they are prepared to quit the sport if the budget cap rules for next year are not seriously revised.
But German Haug, boss of Mercedes' racing programmes, has repeatedly refused to join the rebels, while insisting broad support for the principles of the FOTA alliance.
Some observers have drawn a parallel between Mercedes' softer stance with regards to the FIA position, and McLaren's recent suspended sentence for the 'lie-gate' scandal.
"We still have questions about the regulations and the Concorde agreement," Haug said. "Those questions must be answered before we enrol."
However, Haug stated that it is "possible" the way will be clear for McLaren-Mercedes to enter before May 29.
He said the teams are generally concerned about the extremity of Max Mosley's proposed 40m pounds sterling cap, and that he "understands" the hard line taken by Ferrari.
"You have to see Ferrari with special eyes," said Haug. "And to go from having 1000 people one day, to half (that number) the next is a big step.
"It is easier for example for Williams, so I hope a middle ground can be found," he added.
Haug also insisted that there are currently no active plans for a 'breakaway' championship.