Currently, the second Red Bull-owned team is powered by Ferrari's V8 engine.
But it has been rumoured that, in order for the Faenza based squad and 'big brother' team Red Bull to more closely collaborate in the new V6 era, Toro Rosso could switch to Renault turbos from next year.
At the moment, Renault supplies four teams - Red Bull, Lotus, Williams and Caterham - which is more than any other engine supplier on the F1 grid.
Asked if four is "the ideal number", Renault's Jean-Michel Jalinier told Speed Week: "I don't think there is an ideal number.
"In 2014, we want - if it is necessary - to supply five teams. We are negotiating with the teams and with Toro Rosso.
"We are ready for five teams.
"But three teams would be good for us, making it easier for us to support all of them," he admitted.
Asked if another engine supplier entering F1 would ease the load, Jalinier answered: "Yes. Three is not enough to equip all the teams.
"Five (customer teams) is not my first choice."