Some Renault-powered F1 drivers could run out of engines later in 2014, the French supplier has admitted.
Renault chief Rob White said the French marque's recovery from its early-season struggle for power and reliability is still ongoing.
"At the first test we were miles off. We were in a crisis," he admitted to Germany's Auto Motor und Sport, "but we didn't panic.
"We set up a plan to close the gap. Since then we have made progress but unfortunately not quite enough," White acknowledged.
And those efforts to end the crisis have had a price, he added.
"Within the individual teams, we have consumed more components within the power unit than we had planned. It means that the teams are at different development cycles.
"For some it might be tough to stay within the allowed five units (per driver per season)," White said.
Despite the current problems, however, White is confident Renault can continue to close the gap -- and he insists the horse power advantage held by Mercedes is not even a target too far.
"There is nothing in our engine concept that prevents us from being the best," he said.
However, it has been said that Mercedes stole a march in the fundamental layout of its V6 concept, uniquely situating the turbine and air compressors at either end of the 'power unit'.
White insisted: "It's not that we didn't think of arranging it that way. We don't consider it the match-winner."
Renault's F1 boss Jean-Michel Jalinier agrees: "We have not had any great eye-opening experience in which we had to admit to ourselves that we were caught out."
Rather, White said Renault's 2014 problems have been because "we were late to reach our goals, or because we underestimated the risks or overestimated our capacity to solve the problems in time".