NEW ORLEANS—The nation must get together to fight the violence that is killing thousands of young black men nationwide every year, New Orleans Mayor Mitch Landrieu and Philadelphia Mayor Michael Nutter say.

Last year, 193 people were killed in New Orleans, 331 in Philadelphia and 14,827 nationwide—and most of them were young African-Americans, they said in remarks prepared for a turn-and-turn-about speech Thursday at the National Press Club in Washington.

People murdered in this country from 1980 through 2012 outnumber all U.S. deaths in every war from World War I on, Landrieu said.

He said part of the solution could be for Congress and the president to redirect nearly $14 billion spent to build police departments in Afghanistan, Iraq, Pakistan, Mexico and Columbia to a program to put more police on the beat in cities across America.

"We need to redirect federal resources back to the home front," he said in his prepared remarks. "We need Congress to treat fighting murder and violent crime as a national priority."

After 2,977 people were killed on Sept. 11, 2001, the United States created the Department of Homeland Security and its Transportation Security Administration, and got into "two wars costing thousands of lives and trillions of dollars," Nutter said in his prepared remarks.

But "thousands of black men and boys, and many other Americans die every day in our country and virtually nothing happens," he said.

"This is serious—we need a Domestic Security Agency, because we have a violence problem in America," Nutter said.