Apple Inc. is set to announce next week it's to add Ferrari and Volvo Car Corp to its list of car makers with which it's working to develop and install an on-board operating system, people familiar with the initiative said Saturday.

Apple's announcement will coincide with the opening of the annual motor show in Geneva, which the car industry often uses to show off concept cars and other upcoming technologies.

The car has become the latest battlefield for technology companies because it has the potential of becoming the ultimate mobile device, offering entertainment and information services by keeping passengers connected with the Internet.

Apple's rival Google Inc is working with Audi of Volkswagen AG to develop an on-board system.

Last June, Apple announced its "iOS in the Car" to have the iPhone operate dashboard electronics, using the on-board display for services such as maps and traffic information.

Apple said it expected a dozen car brands to adopt the technology in 2014. It said it already had the support of BMW AG, Daimler AG, General Motors Co. and Honda Motor Co.

Ferrari is a unit of Fiat Chrysler Automobiles NV and Volvo belongs to Zhejiang Geely Holding Group Co. of China.

An Apple spokesperson couldn't be immediately reached for comment.

The Financial Times first reported the news early Saturday about Apple's expected announcement in Geneva.

Ilka Kopplin contributed to this article.

Write to John Stoll at john.stoll@wsj.com, Gilles Castonguay at gilles.castonguay@wsj.com and Colum Murphy at colum.murphy@wsj.com

Corrections & Amplifications

This article was corrected March 2, 2014 at 5:38 p.m. ET to show the proper spelling of the company Apple. The original version of this article incorrectly spelled it Appled.

"Appled Working With Ferrari, Volvo for On-Board Operating System, Sources Say," at 10:03 EST on March 1 misspelled Apple Inc.'s name in the headline. The headline should read: "Apple Working With Ferrari, Volvo for On-Board Operating System, Sources Say.