Fernando Alonso gives no assurances over his future in Formula One

Fernando Alonso has cast major doubt over his Formula One future by publicly refusing to commit to the sport beyond this season.

Alonso is preparing for his home race here at Barcelona's Circuit de Catalunya off the back of his debut victory at last week's World Endurance Championship race at Spa-Francorchamps, Belgium.

But the 36-year-old Spaniard's days of winning in F1 appear further away than ever before as McLaren's troubles extend into another season.

Alonso, who last took to the top step of a Formula One podium at this race back in 2013, may be sixth in the standings after accumulating 28 points from the opening four rounds, but that tally says more about his racecraft rather than the speed of his McLaren.

The British team, having terminated their engine relationship with Honda at the end of last season, had expected to challenge at the sharp end of the grid this year.

But the move to Renault power has provided little joy with Alonso failing to qualify inside the top 10 at any of the four rounds so far.

It has been more than four years since a McLaren car last occupied the top three places, and Alonso, on the eve of what could be his final home race, hinted his future could lie away from F1.

"The biggest thing here is how predictable everything is," said Alonso, who is dovetailing his F1 commitments with six World Endurance Championship events, including next month's prestigious Le Mans 24 Hours race.

"We can put on paper now what would be the qualifying result here on Saturday, what it would be in Monaco, and what it would be in Silverstone. This is sad for Formula One. So that's something you need to take into account for future decisions.

"I'm attempting two world championships at the same time. The F1 calendar is quite demanding."

Alonso could leave McLaren at the end of the year but would give up his pay packet, estimated to be upwards of £20million.

McLaren have brought a series of updates with them to Barcelona in the hope of improved performance, but they will not be alone with the opening leg of the European season kickstarting the development race.

"Normally Spain brings a lot of updates for all the teams so hopefully we can benefit a little bit from that," Alonso added.

"There's still a long way to go for us but at the same time we were here last year with zero points and now we are sixth and fourth in the world championship so in a way it's been a very good start. Let's keep that momentum."