WASHINGTON - Nearly one of every 25 weapons the military bought for Iraqi security forces is missing, a government audit said Sunday. Many others cannot be repaired because parts or technical manuals are lacking.

A second report found "significant challenges remain that put at risk" the U.S. military's goal of strengthening Iraqi security forces by transferring all logistics operations to the defense ministry by the end of 2007.

A third report concerned the Provincial Reconstruction Team program, in which U.S. government experts help Iraqis develop regional governmental institutions. "The unstable security environment in Iraq touches every aspect of the PRT program," the report said.

The Pentagon cannot account for 14,030 weapons, or almost 4 percent of the semiautomatic pistols, assault rifles, machine guns, rocket-propelled grenade launchers and other weapons it began supplying to Iraq since the end of 2003, according to a report from the office of the special inspector general for Iraq reconstruction.

The missing weapons will not be tracked easily: The Defense Department registered the serial numbers of only about 10,000 of the 370,251 weapons it provided. That's less than 3 percent.

The Pentagon spent 3 million on the weapons, and "the capacity of the Iraqi government to provide national security and public order is partly contingent on arming the Iraqi security forces, under the ministries of defense and interior," the report notes. Military officials insisted the weapons either had to be new or never issued to a previous soldier.

By December, the U.S. military had planned to put those weapons in the hands of 325,500 personnel.

Missing from the Defense Department's inventory books were 13,180 semiautomatic pistols, 751 assault rifles and 99 machine guns, according to an audit requested by Sen. John Warner, R-Va., chairman of the Senate Armed Services Committee.

The audit does not make clear at what point the weapons were lost. But it notes that "there could have been undetected losses" before weapons were ever issued to Iraqi security forces, who also lack many needed spare parts, technical repair manuals and arms maintenance personnel.

The second audit, on logistics capabilities, said there is a "significant risk" that the Iraqi interior ministry "will not be capable of assuming and sustaining logistics support for the Iraqi local and national police forces in the near term." That support includes equipment maintenance, transportation of people and gear and health resources for soldiers and police.

Army Col. Brian Baldy, chief of staff for the Defense Department operation in Baghdad training Iraqi forces, told auditors he agreed with most of the report's recommendations to improve weapons accountability. The report calls on the U.S. military to create accurate weapons inventories, fill maintenance positions and tell how to get spare parts.

But he said one recommendation for registering all the weapons' serial numbers was "unattainable" because some of them are foreign-owned. The audit said the military's inventory books also included some weapons that had been donated, captured from enemies or bought with other funds.