Verizon has an LTE network that delivers speeds similar to AT&T's, with wider coverage. Lurie said that by the time AT&T takes over the contract, its LTE network will cover 300 million Americans, or 96 percent of the population. It also has older, slower networks as a backup.
Verizon Wireless said it was looking forward to continuing to provide service to current OnStar customers.
AT&T and GM made the announcement just before the opening of Mobile World Congress, the world's largest wireless trade show, in Barcelona. The companies didn't reveal financial terms. The 6 million current OnStar users pay $19 per month or $199 per year, plus per-minute calling fees. Turn-by-turn GPS navigation costs extra, too.
British automotive research firm SBD believes that 100 million cars worldwide will have built-in wireless capabilities by 2015.
AP Auto Writer Tom Krisher contributed from Detroit.