"In no way will this challenge take away from my main target of Formula 1 with McLaren. In 2018, my aim is to be competitive at every grand prix, and I feel sure that we are closer to achieving that."
Alonso's F1 team McLaren agreed to the deal on the proviso that his Formula One duties come first. Last year Alonso skipped the Monaco Grand Prix to compete at the Indianapolis 500 but he will compete all 21 rounds of the F1 world championship this year.
The only clash in 2018 comes on October 21 when the Six Hours of Fuji coincides with the U.