Kimi Raikkonen lived up to his "Iceman" nickname on Thursday as the outgoing Ferrari driver offered frosty responses to questions over his return to Sauber.

Ferrari confirmed on Tuesday Raikkonen will be replaced by Charles Leclerc in 2019, though the Finn, 38, has decided to remain in Formula One by going back to one of his former teams.

By accepting a two-year offer from Sauber the 2007 world champion has committed to racing well beyond his 40th birthday, much to the surprise of those who expected him to retire after the current campaign.

Asked about his reasons to signing with Sauber at a news conference ahead of the Singapore Grand Prix, Raikkonen replied: "Why not?"

When the question was phrased in a different way, bringing up the move from a title contender to a perennial struggler on the grid, he was a little more willing to talk.

"There are a lot of differences between all the cars. There are not many cars this year that are on the same level. That's how it has always been. We will see what happens in the future," he said.

"Why do you try and make it so complicated? I don't know what will happen, nobody knows what will happen next year when it comes to the speed of the cars. We can always guess, but we will see what we can do.

"I have my reasons [for joining Sauber], and that's enough for me. I don't really care what the rest think."

That was not the end of the cold spell, however, as Raikkonen countered in sarcastic fashion when pressed about his continued passion for racing: "No, I'm not [passionate] actually. It's just pure head games for you guys. I happened to sign, now I'm going to spend two years there not being happy."

Raikkonen did reveal it was Ferrari's choice to end their second stint working together, having rejoined the Italian team in 2014.

"It's not up to me, it's not my decision. Anything after that, though, was my decision," he said.