Verizon Wireless, a joint venture of Verizon and Vodafone Group PLC, asked a U.S. court for a judgment that its advertising claims to be America's Most Reliable 3G Network were truthful, which rival AT&T called misleading on Monday.

In papers filed in U.S. District Court in Manhattan, Verizon said assertions on July 1 by AT&T Mobility LLC, a unit of AT&T, that its advertising was false could not be supported.

AT&T, which has its principal business in Atlanta, had filed the challenge with the National Advertising Division of the Council for Better Business Bureaus.

Verizon Wireless of Basking Ridge, New Jersey said its claims of having America's Most Reliable 3G Network and America's Best 3G Network and America's Most Reliable Wireless Network are truthful, accurate and substantiated and do not violate the trademark law known as the Lanham Act.

It said that AT&T's challenge relies on the incorrect premise that speed is an essential element of the standard for measuring network reliability.

Verizon has long advertised the quality of its network's performance through its Can you hear me now ad campaign, which depicted network testers going from place to place to test call reception.

But rival AT&T said that date network speed was an essential factor for consumers.

Verizon's claim that speed is not a relevant factor to a reliable 3G network is preposterous, AT&T spokesman Mark Siegel said in his statement.

Data network speed is an essential factor to consumers when it comes to data transmission on their wireless devices. The 3G reliability claims made in ads by Verizon Wireless are false and misleading.

The case is Verizon Wireless v AT&T Mobility LLC 09-6656 in U.S. District Court for the Southern District of New York (Manhattan).

(Reporting by Grant McCool and Sinead Carew; Editing by Richard Chang)

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