Pedro de la Rosa fears a lack of sponsorship could keep him out of Formula One next season.
De la Rosa returned to F1 racing with the Sauber team in 2010, scoring six World Championship points before he was dropped in favour of Nick Heidfeld in the wake of the Italian GP.
The Spaniard subsequently joined tyre supplier Pirelli as their test driver for a few days of running and has also been linked to a race-seat with Hispania for next year's Championship.
However, de la Rosa admits a lack of sponsorship is hampering his chances of securing a deal with the backmarker outfit.
"Most of (the available seats) are already spoken for, almost every one, especially for drivers that come with sponsorship," he told Marca.
"That's my handicap, I do not have a sponsor. But I'm not giving up. I'm stubborn and I want to race. If, in the end, I have to be a reserve or test driver, I will, but first I will try everything"
Asked whether a switch to an American series such as IndyCar racing was on the cards, the 39-year-old said: "It is interesting, but, for now, I still think I can compete in F1."
