Their protest capped a week in which transitional government troops retook Mogadishu, Somalia's capital, with the backing of Ethiopian infantrymen.
The U.S. government "gave the green light" to Ethiopia to work in concert with the transitional federal government in Somalia, and that action was "totally wrong," said Hassan Mohamud.
He is the president of the Somali Institute for Peace and Justice in Minneapolis, which organized Saturday's rally.
"We ask the president of the United States, Mr. Bush, and his administration to stop supporting the terrorists. Ethiopian troops are terrorists," Mohamud said to a cheering crowd.
Somali men, women and children gathered Saturday morning in Peavey Park in Minneapolis, and they carried an array of signs. Some said "No more war" and "Islam is the solution."