Sebastian Vettel has refused to commit his future to Formula One after Bernie Ecclestone suggested the four-time world champion could be ready to throw in the towel.

Vettel is under pressure to deliver Ferrari's first world championship in more than a decade.

But the German heads into tomorrow's Chinese Grand Prix on a 231-day losing streak, while it is also uncertain whether he will continue to enjoy the backing of Ferrari as their number one driver.

Vettel's new team-mate, Charles Leclerc, 21, has indicated he could be a contender for the title this season following a strong start to his career with the famous Italian team.

Ecclestone, who is close to Vettel, claimed that the 31-year-old would put his wife, Hanna, and their two young girls before the sport, if he started to feel unloved at Ferrari.

Vettel's £36million-a-year contract with the Prancing Horse expires at the end of next season. Does he envisage being in the sport beyond 2020?

"I don't know at the moment," he said. "I am not going to be in Formula One as long as Bernie was that's for sure, but I hope I am going to be as fit and sharp as he is today when I am 88."

Vettel, still sporting his retro moustache, has also faced criticism for the series of mistakes which have derailed his last two title challenges. In Bahrain two weeks ago he spun – for the fourth time in 10 races – while battling Lewis Hamilton.

"If you analyse all the times he has ballsed up, Lewis has always been involved," said Ecclestone, the sport's former supremo.

"Seb is so desperate to win another world championship, and for Lewis not to win another. When they are side-by-side, Seb suffers from a mental block, which is wrong."

But Vettel insisted: "I feel on top of my game. I am very self-critical and very ambitious. I put a lot of expectation on myself.

"I love driving, I love the sensation of speed, and I love fighting these guys. There are a lot of things I like at the moment and things I would miss, so that is why it is not an option to quit tomorrow.

"But the contract is just a piece of paper. We will see what happens."

Vettel will start behind both Mercedes cars in Sunday's 1,000th Formula One race here in Shanghai after championship leader Valtteri Bottas pipped Hamilton to pole by just 0.023 seconds. Bottas heads Hamilton in the standings by one point.

The Silver Arrows, meanwhile, could be handed a major boost with the return of Niki Lauda, their non-executive chairman, before the end of the season.

The three-time world champion, 70, has been absent from the paddock for almost a year following a lung transplant last summer.

Austrian Lauda, who survived a fireball inferno while racing at the Nurburgring in 1976, then contracted flu on holiday in Ibiza last January and was hospitalised for a second time.

"Niki is on the mend," said Ecclestone. "He wanted to go to the first race in Melbourne.

"I saw him when he came out of hospital. I had lunch at his house, and although he was in a wheelchair, he looked in good shape. But then he caught something because his immune system was weak. He had to start all over again, which is not Niki.

"At the moment he is building up his muscles because he wasn't doing anything for a few months. I am sure he will be back shortly."