The Newspaper Guild-CWA and the American Federation of Television and Radio Artistes on Friday wrote to President George Bush on the second anniversary of an attack by US forces on the Palestine Hotel in Baghdad on 8 April 2003, in which two journalists were killed.
The unions called on the US administration to listen to the requests from journalists around the world for an independent investigation into the record number of deaths among media staff covering the war in Iraq.
The letter was part of a worldwide campaign launched by the International Federation of Journalists (IFJ) and affiliate organisations to keep public focus on the dangers of covering the war in Iraq, they said.
The IFJ is calling for a full and independent investigation by the United States into 14 media deaths in Iraq, including Jose Couso, a reporter with Spain's Telecinco, Taras Protsiuk, a Ukrainian cameraman working for Reuters and Tariq Ayoub, a correspondent for Aljazeera.
"The United States must, however, also defend its traditions of liberty and justice by addressing the concerns of journalists around the world"
President of The Newspaper Guild-CWA
"We recognise, of course, that most journalists who die each year are killed by cruel extremists - and we unequivocally condemn those attacks and the people behind them," said Linda Foley, president of TNG-CWA.
"The United States must, however, also defend its traditions of liberty and justice by addressing the concerns of journalists around the world," said Foley, calling the Pentagon's report into the Palestine Hotel attack "inadequate and unconvincing, raising more questions than it resolved".
The letter came as the US military said on Friday that its forces had detained an Iraqi cameraman they wounded in the northern city of Mosul, thought to be working for US television network CBS.
The Pentagon said the cameraman was arrested and was being investigated as to whether or not he was "more than an observer" of fighter activities, CBS News said in a statement.
The freelance cameraman, who was not named by the network, was shot last Tuesday in northeastern Mosul. The Pentagon said at the time that forces mistook his camera for a weapon and shot him, CBS News said.
CBS News said it was continuing its own investigation into the incident.