Fernando Alonso says he was "not ready" to say goodbye to racing.
Amid his two-year sabbatical, the 39-year-old made his first official visit to Renault's Enstone headquarters on Monday ahead of his 2021 return.
"I know every corner of this place," said the two-time champion. "Every corridor, every door."
It will be Alonso's third stint at Renault, having also raced for Ferrari and most recently for McLaren in 2018.
"When I left F1, my friends told me 'Finally you can do what you want'. But what I want is to race, so I'm going to keep racing," Alonso is quoted by Marca.
"I like racing too much to stop. I don't know what's on the other side of the door, and while it doesn't scare me, I'm not ready to find out yet. I need a steering wheel in my hands every 15 days."