Marussia's Jules Bianchi "will not give up" despite remaining in a critical condition after crashing at the Japanese GP, says his father Philippe.
The Frenchman, 25, suffered severe head injuries when he collided with a recovery vehicle at Suzuka.
"The situation is desperate," said Philippe Bianchi. "Every time the telephone goes, we know it could be the hospital to tell us that Jules is dead.
"He will not give up, I'm sure of that. I can see it. I believe it."
He added in an interview with Italian paper La Gazzetta dello Sport: "I speak to him. I know he can hear me.
"His doctors have told us that this is already a miracle, no one has ever survived such a serious accident. But Jules won't give-up.
F1 drivers formed a 'circle of solidarity' for Jules Bianchi ahead of the Russian Grand Prix
"His trainer Andrea says that if there is one person who can make it happen with his will, it's Jules."
Philippe said the family have been touched by the show of support from other Formula 1 drivers, who gathered at the front of the grid ahead of the Russian Grand Prix, arms around each other's shoulders, forming a 'circle of solidarity' for Jules.
"I've never seen anything like that," said Philippe. "It touched us very deeply. We thank every one of them. So many of them have been in touch, written to me; [Fernando] Alonso, [Jean-Eric] Vergne, [Felipe] Massa have given strong messages.
"Hamilton wrote me a beautiful email in which he says that if there is anything he can do, he's there. Rossi and Marquez from Moto GP too."
Philippe also said that he is using the accident of seven-time world champion Michael Schumacher, who continues his recovery at homeafter suffering a head injury in a skiing accident in December, as a reference point.
The Marussia team paid tribute to injured driver Jules Bianchi ahead of the Russian Grand Prix
"I was very sad when he got hurt," said Philippe. "I kept wondering, like every one else 'Why don't they tell us more about how he is?'.
"But now I'm in the same position I understand. Everyone keeps asking me how Jules is but I can't reply, there is no answer. It's very serious, but he's stable.
"One day he seems a bit better, other days a bit worse. The doctors don't say. The damage from the accident is very bad but we don't know how it will evolve.
"Even with Schumacher it took months to come out of the coma. [FIA president] Jean Todt said he hopes Michael will one day be able to have a normal life. One day I hope we can say the same about Jules."
He added: "It's tough. In a week the life of this family has been destroyed. What are we doing here? Living a nightmare in a place very far from home.
"But when Jules gets a bit better we can transfer him, maybe to Tokyo and things will be a bit easier. But who knows when that will happen. If it will happen. We have no certainties, we just have to wait."