Sister team and former world champions Red Bull Racing also use power units supplied by Renault but carrying the name of watch brand Tag Heuer rather than the French carmaker.
Toro Rosso, who have switched from Ferrari power and finished seventh overall last year, revealed their new STR12 car at the Circuit de Catalunya on Sunday.
"There are still negotiations going on," Tost told Reuters when asked about the engine situation.
"We are free to do this (change the name) and once we have found a partner which wants to do a deal, then we are more than open to negotiate this.
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"It can happen during the season as well."
(Reporting by Alan Baldwin, editing by Peter Rutherford)
