Grosjean and his team-mate Kevin Magnussen are both likely to be confirmed as the Haas drivers for next season after their fairly encouraging first half to this season.
The Frenchman has been tipped to succeed Kimi Raikkonen next season if the Scuderia and the Finn decide to part company.
Though no official contract offer has been disclosed, Grosjean says he is happy to remain with the Haas project.
"It was not such a big surprise for me," Grosjean told the F1 website about Haas' announcement. "I've known this since September 2015! So I would call it a normal continuation. And things are great."
"The team is doing well and I want to help it grow bigger. Of course, if one day there is the chance to be world champion, then great -- when the stars align and you get the chance to drive the car that you want to drive."