The American Federation of Television and Radio Artists and The Newspaper Guild/Communications Workers of America noted that 14 journalists and media staff have been killed by U.S. forces since fighting in Iraq began in March 2003.
The unions' appeal is part of a global campaign by the International Federation of Journalists and affiliated organizations for a thorough investigation into each incident.
Counting killings by the former Iraqi military and insurgents, 64 journalist and media staffers have been killed since the war began. The unions say the war's media casualty numbers are unprecedented compared to other conflicts, even the Second World War.
One of the most controversial incidents was the April 8, 2003, shelling of the Palestine Hotel in Baghdad by a U.S. Army tank that killed cameramen Taras Protsyuk of Reuters and Jose Couso of Spain's Telecinco.
The unions' plea was issued Friday, the second anniversary of the attack.
A Pentagon report released in September 2004 concluded that the tank crew did not know the hotel housed journalists and that coalition forces bore "no fault or negligence" in the deaths." In a letter to President Bush, Newspaper Guild President Linda Foley said the Pentagon's report was "inadequate and unconvincing" and "raised more questions than it resolved."
In a separate report of the Palestine Hotel incident, the Committee to Project Journalists concluded that that attack was not deliberate but could have been avoided with better communications between senior officers and battle units.
Defense Department Press Officer Lieutenant Colonel Joseph Yoswa not seen the appeal and would not comment, but he did say: "We have worked very closely with news media organizations to provide them opportunities to cover our operations in Iraq. Well over 1000 reporters have embedded with our forces over two years. In that time, only three embedded reporters have died due to combat operations. We continue to encourage media to embed with our forces to cover the story. Combat is an inherently dangerous condition to conduct business and we brief our service members about potential media on the battlefield. We have investigated those incidents where we were involved in a reporters death, to include the Palestine Hotel, and we stand by our investigation."