The path has been cleared for Ferrari to supply Toro Rosso with year-old engines next season following a rule change.
Previously a supplier could not provide two different specification engines, but following an FIA meeting in Paris, it was agreed to introduce a new rule on the matter.
"Previously no manufacturer could supply more than one specification of power unit," the FIA said in a statement.
"The World Motor Sport Council was also advised that the FIA had agreed for Ferrari to supply a fourth customer team with a 2015-specification Power Unit in 2016."
While it has not been confirmed, it is widely believed that Toro Rosso will become Ferrari's fourth customer team. The Italian manufacturer currently supplies engines to Sauber and Manor in addition to its own team. From next season Manor will make use of Mercedes engines while newcomers Haas F1 will be powered by Ferrari.
Toro Rosso may have reached an agreement with Ferrari, but it appears that their sister team, Red Bull, will remain with current suppliers Renault despite falling out with the French manufacturer in rather spectacular fashion during the 2015 campaign.