Ferrari chairman Sergio Marchionne believes supplying Red Bul with an engine for the 2016 Formula One season would have been "dangerous" for the Italian team.
Relations between Red Bull and Renault became fraught during 2015 following a string of poor results and reliability issues, with the team searching for an alternative power unit supplier ahead of forthcoming campaign.
Ferrari opted against taking on the role for Red Bull, who agreed to remain with Renault and use engines with TAG Heuer branding.
Marchionne admitted the decision was taken in order to keep the Italian team competitive for the forthcoming campaign.
"We had to cope with some uncertainties of our own architecture and we had to bridge the technological gap," he said.
"So committing to providing an equivalent power unit to a team that has the technical ability to design a high-performance chassis could have been dangerous to Ferrari's competitiveness.
"My main commitment is to support and protect Ferrari. I'm not interested in defeating Mercedes with Red Bull.
"If someone says 'let's use Ferrari's engine so we can defeat Mercedes', I'm not interested in that argument. I want Ferrari to win.
"We know Red Bull's abilities are good, they destroyed us with Sebastian Vettel and the championships they won.
"If we look at Red Bull investing important amounts into their chassis development and then we equip them with a power unit at a certain price reflecting much higher investment than what they pay for, it's inequality on the track. We're not interested in that."