Renault chairman and chief executive Carlos Ghosn has suggested that the French company could pull out of Formula 1, if the sport fails to change how it is governed.
The engine supplier, which partnered Red Bull to four consecutive constructors' titles between 2010 and 2013, has come under fire following the team's poor start to the season.
Renault and Red Bull have been involved in a public spat since the start of the 2015 campaign, but Ghosn has warned F1 that the French marque will not rule out leaving Grand Prix racing.
He told Motorsport.com: "Everything is open. We are really reviewing the situation, we have different options.
"In Formula 1, there are various options that we keep analysing, but it doesn't just depend on us, it also depends on the Formula 1 governing body.
"There's the matter of TV rights, there's the matter of return on investment, but I think by the end of the year, we will take a firm stance."
Red Bull were reported to be in talks with Ferrari recently over a deal to replace Renault as the team's engine supplier.
