Renault will be in Formula 1 "for a long time", according to the French works outfit's former boss.
"We negotiated the return together. I have known for two months," he said.
"We have guarantees that Renault will remain in F1 for a long time, Fernando has his motivation, I'm very happy.
"There was the possibility of going to Racing Point but we preferred to make another choice," Briatore added.
As for 38-year-old Alonso, the two-time champion insists he is not thinking about his Formula 1 return quite yet.
"Right now I am fully focused on the Indianapolis 500," said Alonso, referring to the fabled oval race that has been rescheduled for August 23.
"My goal is to try to do the triple crown, so I'm not thinking about F1 right now. Afterwards I will follow the team and go in the simulator," he added.