By Brad Brooks, Jorge Garcia, Idrees Ali and Phil Stewart LOS ANGELES (Reuters) -U.S. Marines were deployed to Los Angeles on Friday, the military said, in a rare domestic use of its forces after days of protests over immigration raids and as nationwide demonstrations were expected on Saturday,

About 700 Marines assigned to 2nd Battalion, 7th Marines have been ordered to deploy to Los Angeles as protests continue.

Many Mexican Americans remember that California became part of the United States after a 19th century war that cost Mexico more than half its territory.

The Pentagon is scrambling to establish rules to guide U.S. Marines who could be faced with the rare and difficult prospect of using force against citizens on American soil, now that the Trump administration is deploying active duty troops to the immigration raid protests in Los Angeles.

Los Angeles endured a sixth day of protests that have been largely peaceful, mostly contained to a few blocks of the city's downtown area.

The spokesperson told CNN the Marines "have not completed [Standing Rules for the Use of Force] and nonlethal weapons training."

“Constitutionally, as a nation, we do not want to use active duty troops, deploy them against American citizens and others residing in our country. Because the impact is so negative. It makes it appear that the United States of America is a battleground,” Barthel said.

U.S. Marines deployed to Los Angeles to help temper unrest in the city, stopped and detained an American citizen trying to enter a federal building.