Ferrari and Mercedes are pushing for the 2013 engine rules to be delayed, FIA president Jean Todt has admitted.
It emerged recently that the agreed 'greener' four-cylinder turbo regulations no longer had the support of all four of F1's current engine suppliers.
Subsequent reports clarified that only Renault is now fully backing the move.
The FIA announced last Friday that it will now stage "consultations" with the sport's stakeholders and then consider at the end of this month a new "implementation date" for the rules.
Todt admitted to the Spanish newspaper Diario Sport that he finds the situation frustrating.
"It is they who proposed the regulations, and the FIA who accepted them," said the Frenchman.
"The proposal didn't fall from the sky; we had 11 meetings with all the representatives of those involved.
we had 11 meetings with all the representatives of those involved
"When I talk to those responsible at Renault they tell me they will go out of F1 if this new engine does not come in 2013. When I talk to Mercedes and Ferrari they ask me to postpone the introduction for a couple of years.
"They are not against the rules but want them postponed. So in the coming days I will keep up the contacts personally to see where we are," added Todt.