FIA president Jean Todt is set to meet yet again with the engine manufacturers on Monday.
The Frenchman is under pressure from Ferrari, Cosworth and Mercedes about his plans for the four-cylinder turbo formula for 2013.
Renault is keen on Todt's plan, but - in light of the opposition, powered by F1 chief executive Bernie Ecclestone - Ferrari has thrown a spanner in the works with a proposal for V6 turbos.
It is suggested the manufacturers will argue that a V6 can only be designed in time for 2015.
Monday's talks in Paris take place in the shadow of next Friday's meeting of the World Motor Sport Council; reportedly the last opportunity to amend the 2013 rules.
"The FIA can achieve its goals with a V8 with KERS and limitted fuel flow," Cosworth's Mark Gallagher is quoted by Auto Motor und Sport.
"Downsizing to four cylinder does not necessarily save fuel or is green," he added.
Todt told the BBC on Sunday: "There's a lot of discussion at the moment but I'm looking for a lot of harmony for the future."