President Trump signed a proclamation to ban travel from certain countries, citing national security risks. It's set to take effect at 12:01 a.m. Monday.

A sweeping new travel ban on citizens from a dozen nations was announced by the White House on Wednesday, reviving a defining effort from the first Trump administration to crack down on entries from specific countries.

Here is a closer look at why the administration says it is instituting full bans on foreign nationals traveling to the U.S. from 12 nations.