Kimi Raikkonen has hinted he wants a new deal at Ferrari for 2019.
Charles Leclerc and Daniel Ricciardo are linked with the Finn's seat, but Sebastian Vettel has made clear he wants his friend Raikkonen to stay.
"I think he's fast enough compared to anyone out there," the German told La Gazzetta dello Sport.
"Ferrari may find it easy to find a driver, but it's much more difficult to find someone with the same values and respect," he added.
Raikkonen, 38, was coy when asked if he wants to stay.
"It's not my decision," he said. "It depends on the team and they know exactly what I want. I do not drive in formula one if I do not have fun," he said.
"The pleasure of driving is the only thing that keeps me here. I can do without everything else, even though it's the way it is.
"The decision is influenced by many things, but at least my passion for racing will not disappear from this moment to the end of the season," Raikkonen added.
Bahrain International Circuit - Winter testing