WASHINGTON—The Trump administration is planning to invoke a sweeping wartime authority known as the Alien Enemies Act in an effort to speed up deportations, according to an official familiar with the discussions.

President Donald Trump is expected to use an 18th-century law, the Alien Enemies Act of 1798, to hurry along his mass deportation effort. Trump has made deporting illegal immigrants, especially members of criminal organizations such as Tren de Aragua,

The Alien Enemies Act is a wartime law passed in 1798 as part of the Alien and Sedition Acts under President John Adams. It grants the U.S. president the authority