The FIA has handed Ferrari the approval to supply a 'fourth team' with a 2015 specification power unit, which is set to be supplied to Scuderia Toro Rosso.
The Italian team is currently without an engine following sister team Red Bull Racing's initial decision to ditch its current agreement with Renault, even if a turnaround means the former title winners are set enter a revised contract that will see it continue to use the French firm's power units but take charge of its own development.
Indeed, Red Bull Racing had originally sought an engine agreement with Ferrari, but turned down the offer deal after the Italian team refused its condition of development parity with the works outfit.
Despite this, Ferrari did extend its offer of a year-old engine to Toro Rosso, which it is subsequently set to take up now the World Motor Sport Council has confirmed approval of a 'fourth customer team with a 2015-specification Power Unit in 2016'.
Ferrari required special dispensation as it cannot supply two different specifications of power unit without clearance.
The deal will see STR return to the Ferrari stable having worked with the manufacturer from its 2006 debut to the end of 2013 when it was brought into line with Red Bull by taking on Renault power units.
It will make STR its fourth customer alongside Ferrari itself, Sauber and the incoming Haas team.