The Republican chairman of the Senate Armed Services Committee asked Defense Department officials yesterday to brief lawmakers on the nature of a U.S. military program that arranged for positive stories about the war, written by U.S. troops, to be published in Iraqi newspapers under the guise of independent journalism.

Sen. John W. Warner (R-Va.) said he has not been able to confirm or refute reports that the U.S. military was using a government contractor to pay Iraqi media outlets to run favorable stories about the war and the rebuilding effort, but he said he is concerned about any actions that could undermine U.S. credibility overseas.

"Further, a free and independent press is critical to the functioning of a democracy, and I am concerned about any actions which may erode the independence of the Iraqi media," Warner said in a written statement.

White House spokesman Scott McClellan said yesterday that the Bush administration is "very concerned" about reports that U.S. troops might have been planting news stories in the Iraqi press, and Pentagon officials said they are working to learn key details about the effort. Military officials in Baghdad confirmed the existence of the program this week after the Los Angeles Times reported that Iraqi newspapers had accepted payments to run positive stories written by the U.S. military and distributed by a government contractor.

Military officials said the program was designed to give the Iraqi people factual information in order to counter insurgent claims about the war. Information operations soldiers would craft the material before it was sent to Lincoln Group, a Washington-based contractor hired by the military to aggressively promote the U.S.-led coalition by targeting Iraqi media outlets.

In Baghdad yesterday, Maj. Gen. Rick Lynch, the top U.S. military spokesman in Iraq, responded to a question about the planted stories by saying: "We don't lie. We don't need to lie. We do empower our operational commanders with the ability to inform the Iraqi public. But everything we do is based on fact, not based on fiction."

Lynch quoted a senior al Qaeda leader, Ayman Zawahiri, as having told Abu Musab Zarqawi, the main terrorist leader in Iraq: "Remember, half the battle is the battlefield of the media."

An Army officer who worked in Iraq last year said there was increasing pressure in late 2004 to promote "good-news stories" and that there was a growing divide between the public affairs officers and the "information operations" officers about how to get the message out. In some cases, the officer said, Iraqis were hired by U.S. forces to write stories that would be sent to Iraqi newspapers, but the source of the stories was always clear. The planted stories, by contrast, were presented to newspapers by people posing as freelance journalists, and the source of the material was hidden.

The officer, who spoke anonymously because he was not authorized to discuss the program, said American employees of Iraqex -- Lincoln Group's former name -- arrived in Baghdad in 2004 under a multimillion-dollar contract and aggressively sought to get involved in influencing the Iraqi media. The officer said Iraqex took the military's ideas and then embellished them.

Finer reported from Baghdad.

Sen. John W. Warner voiced concerns about Iraqi media independence and U.S. credibility abroad.