WASHINGTON - The Pentagon has lost track of about 190,000 AK-47 assault rifles and pistols given to Iraqi security forces in 2004 and 2005, according to a new government report, raising fears that some of the weapons have fallen into the hands of insurgents fighting U.S. forces in Iraq.

The report from the Government Accountability Office indicates that U.S. military officials do not know what happened to 30 percent of the weapons the United States distributed to Iraqi forces from 2004 through early this year as part of an effort to train and equip the troops.

The United States has spent $19.2 billion to develop Iraqi security forces since 2003, the GAO said, including at least $2.8 billion to buy and deliver equipment. But the GAO said weapons distribution was haphazard and rushed and failed to follow established procedures, particularly from 2004 to 2005, when security training was led by Gen. David Petraeus, who now commands all U.S. forces in Iraq.

The Pentagon did not dispute the GAO findings, saying it has launched its own investigation and indicating it is working to improve tracking. Although controls have been tightened since 2005, the inability of the United States to track weapons with tools such as serial numbers makes it nearly impossible for the U.S. military to know whether it is battling an enemy equipped by American taxpayers.

'They really have no idea where they are,' said Rachel Stohl, a senior analyst at the Center for Defense Information who has studied small-arms trade and received Pentagon briefings on the issue. 'It likely means that the United States is unintentionally providing weapons to bad actors.'

One senior Pentagon official acknowledged that some weapons probably were being used against U.S. forces.

Stohl noted that the Bush administration complains that Iran and Syria are supplying insurgents but has paid little attention to whether U.S. military errors play a role. 'We know there is seepage and very little is being done to address the problem,' she said.