Next year, you may be able to add your car to your phone plan.

AT&T and General Motors said on Monday that they were working together to add wireless service in 2014 to most Chevrolet, Buick, GMC and Cadillac vehicles in the United States and Canada.

The companies have not determined how much the service will cost, but AT&T said it would make its latest network technology, 4G LTE, available for the vehicles.

Glenn Lurie, AT&T’s president of emerging enterprises, said adding a wireless connection inside cars would open doors to a wave of new apps that make vehicles smarter. AT&T and GM plan to develop some apps together, as well as allow outside software developers to contribute.

“The car is going to be a smartphone with four wheels,” Mr. Lurie said in an interview. “The opportunities are endless when you think about adding an LTE pipe to a car.” He said potential apps might display real-time traffic on a map or perform enhanced vehicle diagnostic, giving consumers a deeper understanding of what is happening inside their cars. Children sitting in the back seat might be able to stream Netflix over the wireless connection.

The partnership is another move by AT&T to find new revenue beyond phone plans. In March, it is to release a connected home security system called Digital Life. Mr. Lurie said he believed the connected car would be AT&T’s “next billion dollar business.”