Toro Rosso expects to seal F1 engine deal for 2016 'within weeks'

That follows a recent meeting in Geneva involving all four engine manufacturers and the FIA during which the way was cleared for the use of year-old spec power units.

With Toro Rosso, along with Red Bull, poised to split from Renault at the end of the season, it is understood the former is set to rekindle its previous partnership with Ferrari.

"We are still negotiating, and we are getting closer and closer, and within the next weeks we will have a decision," Tost told Autosport.

"I hope it will be before the end of the season because otherwise it will become very tough for the start in Melbourne, especially as the calendar has changed and it [the start] is two weeks earlier than before."

Todt added that the possibility to run with a year-old engine "helps us out".

He said: "The manufacturers decide what we get, and in the end we have to be happy to get something.

"If it's one year old, this is how it is. The influence we have in this case is not on a level we maybe would expect, or wish.

"Therefore with this regulation and this situation we have to take what they offer us."

Tost also sees no reason why Max Verstappen and Carlos Sainz Jr will not form his driver line-up for next season.

The young duo again performed superbly during the United States Grand Prix to finish fourth and seventh and move the team to within seven points of sixth-placed Lotus in the constructors' standings.

"They are doing a fantastic job," said Tost.

"I'm looking forward to next year when I hope everything works out as I wish.

"It's not decided yet, but I hope this is the case and we can continue with both of them.

"I am convinced [technical director] James Key and his technical team will create another very competitive car for next season, therefore I am looking forward to the future."