UPDATE 1-AT&T sues Verizon Wireless over 3G ads

* Wants stop to use of "misleading" maps in Verizon ads

* Says ads are causing "incalculable" market share loss

* Asks for temporary restraining order

NEW YORK, Nov 3 - AT&T Inc is suing Verizon Wireless in an effort to stop its bigger mobile rival from using "misleading" coverage maps in ads that AT&T says are causing it to lose "incalculable market share."

According to the lawsuit, which AT&T said it filed in Atlanta federal court, a recently launched ad campaign shows maps with white spaces that mislead consumers into thinking AT&T has no network coverage outside of areas where it offers high-speed mobile services, known as third-generation or 3G.

But AT&T argued that its customers can "fully use their wireless devices outside of a '3G' coverage area and undisputedly have coverage in areas depicted by white or blank spaces on the maps used in Verizon's advertisements."

It asked the court for a temporary restraining order against Verizon Wireless, a venture of Verizon Communications Inc and Vodafone Group Plc, so that its rival cannot benefit from the ads while the court sets a date for a preliminary and permanent injunction hearing.

"Verizon has stepped over the line of legitimate comparative advertising," AT&T said in an emailed copy of the the lawsuit, which was not immediately available online.

The case is AT&T Mobility LLC v. Cellco Partnership, U.S. District Court, Northern District of Georgia.