General Motors Co.’s driverless-car business, Cruise, will delay the roll out of an autonomous ride-hailing service scheduled for late this year, underscoring the difficulty of safely deploying robotic vehicles on public roads.

Cruise Chief Executive Dan Ammann said the company needs to log more test miles on its driverless electric cars, which have been plying San Francisco streets for more than three years with safety drivers at the wheel. He declined to give a new timeline for beginning a commercial service, which he said...