By the end of the year, the Twitter Alerts program will allow police departments and groups like the Red Cross to send out tweets during an emergency through a special account.
Twitter says alerts will also be marked with an orange bell icon to differentiate them from regular tweets.
The move follows a feature called "lifeline", which Twitter launched in Japan last year. It underscores the services' growing role in delivering fast information in an emergency.
(The Associated Press contributed to this report)