Sebastian Vettel has indicated that he has not given up on clinching the 2018 world championship title.

According to I, the highly influential Italian sports daily, the driver said "Ciao Mondiali" to his hopes in Singapore.

It means goodbye to the world championship, but neither the German driver, his Ferrari boss, or his former chief at Red Bull agree that it is quite over yet.

Vettel fell a full 40 points behind Mercedes's Lewis Hamilton in Singapore, but Ferrari boss Maurizio Arrivabene said that with six races still to go, the Maranello team will not give up.

"Nothing is lost," he insisted. "We'll be calm and determined for the last races and fight to the end."

Christian Horner, Vettel's former boss at Red Bull where he won all of his four previous titles, agrees with Arrivabene about the German driver's fighting qualities.

"I think he was 40 points down in 2012," the Briton is quoted as saying by Brazil's Globo.

"Ferrari has a very fast car and there are 150 points available. Obviously it looks as though Lewis is in charge, but Seb is very good under pressure and certainly will not give up."

Vettel confirmed that hypothesis, telling Germany's Sport Bild that he has not forgotten how he won his earlier four world championships.

Asked how he can win again in 2018, Vettel answered: "First, because I can. I've proved it four times.

"Second, because we have a car that is on par with Mercedes.

"Singapore didn't help. It's disappointing if you can win races and you do not. But I still think we can only beat ourselves.

"I can still become world champion with my own power and so I'll continue to fight."

Some think that Vettel loses his head or is too aggressive in the heat of a world championship fight, but the 30-year-old insists that is not the case.

"My driving style has given me four world titles and 52 victories," Vettel told Auto Bild.

"Everyone is afraid to fail, and I'm as aware as anyone that sometimes when you risk, it goes wrong. But you can't let it paralyse you.

"Ayrton Senna said that if you don't go for a gap anymore, you're not a racing driver, and I agree. The same applies to risky strategies as we saw in Singapore. I will always defend my team.

"If we win every race from now on, we are safe. That must be the goal from now on."

The championship continues next weekend with the Russian Grand Prix.