Increasingly, carrying a smartphone means being a target. Commuters who doze on public transit are targets for pickpockets, while pedestrians chatting on iPhones attract armed muggers.

Police officials hope their newest resource -- a voluntary agreement between the Federal Communications Commission and mobile service providers to disallow service to phones that are reported stolen -- will help stem the tide. Officials said Tuesday they believe the ability to render phones nearly useless will eliminate the profit motive for robbery and theft of mobile devices.

"Any system that can prevent a theft or a thief from reselling a device will be a welcome tool to make our system safer," said D.C. Metro Transit Police Chief Michael Taborn.

New York Police Commissioner Ray Kelly called the database akin to "draining a swamp to fight malaria."

More than half of the robberies reported to the D.C. police since last fall involved smartphones, according to Police Chief Cathy Lanier, whose department has taken to undercover stings and increased patrols to target rising robberies and thefts.

In recent months, Lanier joined New York officials and other big-city police chiefs to lobby Federal Communications Commission Chairman Julius Genachowski in hopes of convincing service providers to take the step announced Tuesday.

Wireless carriers -- including AT&T, T-Mobile, Verizon and Sprint, which serve 90 percent of smartphone users -- agreed to implement a database of unique identification numbers embedded in phones. When a victim reports a stolen phone, its number will be placed in a database and service will be denied the next time someone tries to use the device, officials said.

"Working together, we have come a long way in a short time," Genachowski said.

Philadelphia Police Commissioner Charles Ramsey, president of a national police chiefs association, said he hopes the database will help make streets safer.

"In most instances, these devices are being taken at the point of a gun," said Ramsey. "I'm thinking this is going to make a difference across the U.S."

Wireless carriers said they will launch the database in six months. Genachowski said that if they do not, regulators might seek legislation requiring it.

The database is not a cure-all, admitted Sen. Charles Schumer, D-N.Y.: Savvy thieves can "wipe" the phones' unique ID numbers, making them operable again. Schumer plans to introduce legislation that would make such modifications a federal crime.