Antonio Giovinazzi has insisted that Formula 1 remains his "priority".
With the support of Ferrari, the Italian made his F1 debut early last year as he temporarily replaced the injured Sauber driver Pascal Wehrlein.
Yet for 2018, it was Ferrari's other junior - new F2 champion Charles Leclerc - who got the green light for the full-time Sauber seat.
Giovinazzi will now have a reserve and occasional Friday practice role, but he notably tested recently for the Virgin Formula E team.
"The car is very different from everything I was used to before," the 24-year-old told Italy's La Gazzetta dello Sport.
"It has less downforce so braking must be more accurate. In my opinion, the day went well."
However, Giovinazzi denies that the test indicates that Ferrari is ushering the Italian driver into Formula E rather than continue to steer him towards F1.
"It was my personal initiative," he insisted. "Ferrari did not participate in it.
"I wanted to understand how everything works in Formula E, because there's nothing better than driving a racing car. But my priority remains Formula 1. I will do everything to get a place in one of the teams."
Giovanazzi confirmed that he will be Sauber's reserve and occasional Friday practice driver in 2018.
"The rest of the time I will try to be as useful to the team as I can," he said.
The new season gets underway in March.
