Reuters international news agency made an official complaint in a letter to a US senator on Wednesday.
The news agency complained of "a long parade of disturbing incidents whereby professional journalists have been killed, wrongfully detained and or illegally abused by US forces in Iraq".
In the letter to Virginia Republican Senator John Warner, head of the US Senate Armed Services Committee, Reuters slammed the Pentagon for failing to safeguard journalists covering the conflict, describing the situation as "spiralling out of control".
Senator Warner was urged to call upon US Secretary of Defence Donald Rumsfeld to resolve the issues "in a way that best balances the legitimate security interests of US forces in Iraq and equally legitimate rights of journalists in conflict zones under international law".
The increasingly risky conditions journalists were forced to work in limited their "abilities to do their jobs" and created "a serious chilling effect on the media overall", the letter said.
Reuters also accused US forces of "unduly preventing US citizens from receiving information ... and undermining the very freedoms the US says it is seeking to foster every day that it commits US lives and US dollars".
According to Reporters Without Borders, 68 journalists and media workers have been killed in the Iraq conflict since March 2003.
US forces have admitted killing three Reuters journalists, most recently Iraqi soundman Walid Khaled, who was shot by troops on 28 August while on assignment in Baghdad.
According to the US military, the soldiers' actions had been justified.
The news agency also believes a US sniper was responsible for the death of a fourth Reuters journalist in Ramadi, west of the Iraqi capital, last year.
The US military has repeatedly refused calls to carry out an independent inquiry into the deaths of the Reuters' journalists, handing over responsibility for investigations to the military units involved, who subsequently exonerated their soldiers, the agency said.
The letter said Reuters and other international news organisations were concerned by the "sizeable and rapidly increasing number of journalists detained by US forces".