Fernando Alonso says he still has not decided what he will be doing in 2019.

Frustrated with modern F1 and the top teams' apparent refusal to sign him, the double world champion is quitting the sport at the end of the year.

The Le Mans winner in 2018, Alonso is reportedly now weighing up a programme that could involve sports cars, Indycar and perhaps even Nascar for 2019.

"A few days have passed since Japan and since then nothing has changed," the 37-year-old told Spanish news agency EFE.

"I have not made a decision but I have many options."

One of them is definitely Indycar, and if that is a possibility, so too is a full McLaren team entry in the top American open wheeler series.

"Will they be able to create another team so they can compete not only in formula one but also Indycar? I don't know, it's better to ask them," Alonso said.

"For me it is necessary to carefully analyse the opportunities and compare calendars and find out what preparatory work needs to be done, because any programme for next season requires preparation.

"This is a very serious and complex project," he insisted.

"I hope I can decide soon but I don't know how long it takes to get everything ready but for sure it takes time."

One of Alonso's best friends from his time in F1 was Mark Webber, and the Australian said he hopes the current McLaren driver knows what he is doing.

"I would not particularly like to do Indycar because it's dangerous and the guys there have a lot of experience," Webber told Marca sports newspaper.

"Yes he did a great job last year at the 500 but I just hope he knows when to stop, although I'm not the one to tell him," he added. "He's a big enough boy to know that.

"But in my view his decision to leave F1 is correct. It was the right time to go," Webber said.