Research In Motion Ltd.'s BlackBerry service was disrupted in North America, affecting all carriers in the region, according to AT&T Inc.

AT&T, the biggest U.S. phone company, learned of the disruption from Research In Motion at 3:30 p.m. New York time, Fletcher Cook, a spokesman for AT&T in San Francisco, said in an interview today.

The problem is affecting all carriers and isn't with AT&T's wireless network, Cook said. Research In Motion, based in Waterloo, Ontario, has more than 12 million BlackBerry subscribers, most of them in North America.

Users won't be able to send or receive messages or browse the Web, Research In Motion said in an e-mail to customers today. The company cited a problem with a ``component of the Americas network infrastructure.''

Research In Motion hasn't said when the problem will be fixed, Cook said. Verizon Wireless spokeswoman Nancy Stark also said the glitch is with Research In Motion. Marisa Conway, a Research In Motion spokeswoman, didn't immediately return a call seeking comment.

Last year, a malfunction in newly installed software led to disruptions in the BlackBerry service, shutting off Internet access across North America. In that incident, a switch to a backup system led to further delays.

Increased Competition

Service interruptions raise investor concern that customers will look to rival service providers, analysts such as Nomura International Plc's Richard Windsor have said. Nokia Oyj and Motorola Inc. introduced new devices and have acquired e-mail service providers in the past three years to challenge Research In Motion.

AT&T, Verizon Wireless and other phone companies pay Research In Motion for each subscriber that uses BlackBerry e- mail. The fee is about $6 a month, estimates Goldman, Sachs & Co. analyst Brantley Thompson.

Research In Motion dropped $1.12 to $93.35 in extended trading. The stock gained $4.76 to $94.47 at 4 p.m. New York time on the Nasdaq Stock Market. The shares have more than doubled in the past 12 months.

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