An Amtrak engine sits on the tracks at Union Station in Washington, July 25, 2012. Amtrak, the U.S. passenger rail service, plans a $7 billion expansion of Washington, D.C.'s Union Station with the goal of making it a high-speed rail and commercial hub. (JONATHAN ERNST/REUTERS)

A 27-year-old District man admitted in federal court Tuesday that he made two bomb threats that ended up snarling Amtrak trains for hours.

Michael Jerome Dennis pleaded guilty to a charge of threatening and conveying false information about the threatened use of a destructive device. Under federal guidelines, Dennis faces 18 to 24 months in prison at his sentencing on Nov. 9.

Authorities said that Dennis called Amtrak’s communications center on Nov. 30 and Jan. 19, claiming to have placed a bomb on the New York Avenue NE bridge, which spans train tracks near Union Station.

The threats were bogus, but they had forced officials to halt train traffic while they checked for explosives. More than 1,000 rail passengers were affected by the delays, authorities said.

U.S. Attorney Ronald C. Machen Jr. has said that prosecutors take such threats seriously because “they cause delays, distract attention from real public safety concerns, and instill unnecessary fear in the traveling public.”