WASHINGTON (Reuters) - 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 (FEMA) said in a statement this week. 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." The test has been scheduled to ensure that the alert system would work in the event of a national emergency. U.S. cellphone users will not be able to opt out. Former President Barack Obama signed a law in 2016 requiring FEMA to create a system allowing the president to send cellphone alerts regarding public safety emergencies. Since the wireless emergency alert system began in 2012, it has issued over 36,000 alerts for situations such as missing children, extreme weather and natural disasters, but never a presidential directive. Cell phone users can opt out of natural disaster or missing children alerts.