"Active duty elements are postured on military bases in the National Capitol Region but are not in Washington, D.C.," Pentagon spokesman Jonathan Rath Hoffman said in a statement.
He said the troops were on "heightened alert status" but "are not participating in defense support to civil authority operations."
Protests have swept US cities, including Washington, D.C., since the May 25 killing of George Floyd, a 46-year-old African American who died after a white policeman pinned his neck under a knee for nearly nine minutes in Minneapolis on May 25.