A new emergency alert system that sends notifications to cellphones in the event of a disaster or terrorist attack will be implemented in New York and Washington by the end of this year, officials said.

Mayor Michael Bloomberg on Tuesday unveiled PLAN, the Personal Localized Alerting Network, which is expected to provide residents with timely information "alerting them to imminent safety threats in their area."

Mobile phone users will receive "geographically targeted, text-like messages," according to a written statement from the Federal Communications Commission.

The network was made possible by a 2006 Congressional bill called the Warning Alert and Response Network Act.

Mobile customers will receive three types of alerts containing 90 characters or less, ranging from presidential alerts to child abduction bulletins.

Phone carriers may allow subscribers to block all but presidential alerts, officials said.

A special chip is needed to allow phones to receive the notifications, though many "smart" phones already have the new technology, said FCC spokesman Neil Grace.

The system will also be able to send messages when cellphone towers experience high traffic.

High traffic and downed cellphone towers were considered primary reasons for service disruption in New York in the aftermath of Sept. 11 attacks.

PLAN is expected to be expanded to the rest of the country by April 2012, according to commission Chairman Julius Genachowski.