By Omar Younis, Brad Brooks, Phil Stewart and Idrees Ali LOS ANGELES (Reuters) -U.S. Marines deployed to Los Angeles made their first detention of a civilian on Friday, the military said, part of a rare domestic use of its forces sent to the city after days of protests over immigration raids.

The troops are authorized to detain people who pose a threat to federal personnel or property, but only until police can arrest them.

Cities large and small were preparing for major demonstrations Saturday across the U.S. against President Donald Trump, as officials urge calm, National Guard troops mobilize and Trump attends a military parade in Washington to mark the Army’s 250th anniversary.