The Trump administration will send a message to all U.S. cellphones on Thursday to test a previously unused alert system that aims to warn the public about national emergencies.

The messages will bear the headline "Presidential Alert," the Federal Emergency Management Agency said. Phones will make a loud tone and have a special vibration, said FEMA, which will send the alert.

The test message, scheduled for 2:18 p.m. EDT on Thursday, will read: "THIS IS A TEST of the National Wireless Emergency Alert System. No action is needed."