Fernando Alonso teased a potential return to the Indianapolis 500 at the United States Grand Prix, while defending Formula One champion Lewis Hamilton suggested he would prefer to try racing in NASCAR.
Retiring F1 star Alonso competed in the Indy 500 last year and was then part of the winning team at the 24 Hours of Le Mans earlier in 2018, with speculation building as to where he will race next year.
The Spaniard admitted that a return to the United States is on the cards, but he would not commit to taking part in the Indy 500 when quizzed in Austin.
"I don't have 21 races in F1 to travel around. With more free time, I will come to the States for a holiday," Alonso told a news conference. "Maybe a bit more...
"Let's see. The Indy 500 is very attractive - as it was last year. After winning Le Mans this year, it is even more attractive to achieve it in the short term.
"I'm still working on a plan for next year. As soon as it's finalised, you will know."
When Hamilton was asked if he might be interested in the Indy 500, he said he was more intrigued by NASCAR, although he is not yet sure if he will continue racing beyond his F1 career.
"I would definitely like to try [the Indy 500]. I've never really driven an oval before, the cars are really fast and I'm always looking to go faster," Hamilton said.
"I'll probably get the chance to have a go. I'm sure if I wanted to have a go, I could. It's never been a series, in Europe, that you grew up aspiring to be in - it was always Formula One. The thought was that this was the highest grade of drivers.
"I think I'd prefer to try NASCAR. Watkins Glen - I've always wanted to have a go out there, big hands to the side. I have driven at NASCAR years ago, at Watkins Glen, so that's something which was awesome.
"That's something I potentially could do. I honestly have no desire to do any other racing beyond Formula One, but that may change when you do stop.
"You do it your whole life and the temptation is always going to be there - I'm always going to be a racing driver at heart."