Fernando Alonso has admitted he could return to Formula 1 in 2020.

The new back-to-back Le Mans winner will not return to the world endurance championship next year, and now he has told the Italian magazine Man In Town that the F1 door remains open.

"If F1 becomes an attractive option again, there is no doubt that I would go back," said the 37-year-old Spaniard.

Zak Brown has ruled out a 2020 seat at McLaren for Alonso, but the two-time world champion is believed to be eyeing a cockpit at one of the top three teams.

"I had contact with Mercedes in 2016 when Nico Rosberg decided to retire," Alonso revealed. "I talked to Toto Wolff but in the end we did not reach a definitive yes. I was at McLaren and it was not easy to find a solution.

"In the future I am open to interesting proposals. If I decide to return to F1 it is only if there is a real chance of winning the world championship.

"I am not interested in projects that start from scratch. I want a winning car right away."

There are even rumours of an unlikely return to Ferrari.

When asked what advice he would give his former employer at Maranello, Alonso said: "Patience.

"It's not easy when you are expected to win every weekend, and Ferrari is the best known and most loved team in the world.

"When I was there we lacked the skills and technical resources but we were competitive. Now the car is very competitive but the climate of excessive pressure does not help. And then the Mercedes is very strong," he added.