THE SIDELINES : Prost Extends Ferrari Contract

MARANELLO, Italy — Three-time Formula One champion Alain Prost, who had been thinking of quitting auto racing, extended his contract with the Italian team Ferrari through 1992, racing sources reported today.

Ferrari officials did not immediately confirm the report, but a communique from the team about Prost is expected in a few days.

Ferrari, which is owned by the Italian auto giant Fiat of Turin, held an option on the 35-year-old French driver through 1991.

But Prost, embittered by the loss of this year’s world title after a controversial crash with Brazilian rival Ayrton Senna during the Japanese Grand Prix, had said recently that he was uncertain whether to continue racing.