Ferrari has admitted that it is important to have a third team running its engine when the new 1.6-liter turbocharged V6 engines are introduced next year.
It is likely to continue its alliance with Sauber next year, even though a deal has not been done, but Scuderia Toro Rosso is planning to switch to Renault. Ferrari is known to have held talks with Force India about a possible deal, although the Silverstone squad could also continue with Mercedes engines.
The engine supply deal negotiations are related to the team's driver decision, with both Ferrari-contracted Jules Bianchi and former Force India driver Adrian Sutil, whose nationality would suit Mercedes, in contention and testing at Barcelona this week.
With engine mileage likely to be at a premium next year despite plans to allow an early V6 track test this year, Ferrari risks being at a disadvantage if it doesn't secure at least two customer teams.
"Customer teams are a very important opportunity for an engine supplier," said Ferrari's head of engines Luca Marmorini when asked how important it was to have a second customer team when the new power units come in.
"First of all, we can test more engines and now we can't test during the season, we can collect much wider data. It's also important to have a reference with cars using the same engine and have a good relative pace. So Ferrari is strongly committed to supplying a good engine to customer teams."
Marmorini added that the relationship with Toro Rosso is still good and that he is still open to continuing the supply deal. Toro Rosso has used Ferrari engines since 2007, when it took over the supply run by sister team Red Bull a year before.
"I don't know if Toro Rosso will be with us next year," said Marmorini. "We are still working very well with them now. They're an important contribution to Ferrari engine development, but I also think we are giving them a competitive engine."