But the BlackBerry uses highly encrypted data that is received by wireless carriers’ towers and is immediately routed through a closed, global network operated by the company. To enforce the ban, the carriers will stop forwarding that data.

Because of this level of security, the United States government allows many military and law enforcement employees to send confidential messages by BlackBerry, but it also makes surveillance correspondingly difficult.

As a result, R.I.M. officials have clashed with officials elsewhere in recent years.

In 2008, security agencies in India suggested that BlackBerry service might be shut down there unless R.I.M. installed servers in that country to allow them to intercept messages. The company refused, but sent representatives to meet with the Indian government. Indian regulators, while expressing reservations, have said they have no plans to restrict the service.

Analysts and telecommunications experts also believe that security concerns delayed the arrival of BlackBerry service in China. It is unclear what actions the company took, if any, to alleviate those worries.

There were conflicting reports Sunday about whether Saudi Arabia had also decided to ban the BlackBerry services. Some news agencies cited an interview with a Saudi Telecom official on the Al Arabiya television network that confirmed the decision, but in other Al Arabiya news reports company officials denied the service would be blocked

The Saudi authorities released no official statement, and an adviser to the Saudi government, speaking on the condition of anonymity, said no decision had been made as far as he knew. But one prominent Saudi economist, Ihsan Ali Bu-Hulaiga, said “it seems to me a number of other countries in the region will follow the lead of the U.A.E.” for the same security-related reasons.

In the emirates, concerns are also fueled by the fact that native Emiratis are a minority there, and the government regards electronic surveillance as an important tool against would-be terrorists, swindlers and other potential troublemakers drawn to the country’s relatively unfettered environment.