WASHINGTON (AP) -- The White House is preparing the country for the first nationwide test of the country's emergency alert system on Wednesday.

The test will occur at 2 p.m. EST Wednesday and will last about 30 seconds, presidential spokesman Jay Carney told reporters.

The alert system can be activated by the president to inform the public in times of emergency. It has already been tested and used on the local level.

Carney said everyone should remember about Wednesday's action by the administration: "It's just a test."