The US military has failed to keep track of thousands of weapons shipped to Afghanistan, leaving them vulnerable to being lost or stolen, a report says.

The report has been compiled by congressional auditors, the US Government Accountability Office (GAO).

It found that, in the four years up to June 2008, the US military failed to keep complete records on some 222,000 weapons entering the country.

The report will be discussed in the US House of Representatives on Thursday.

It states that weapons supplied by the US to the Afghan military "are at serious risk of theft or loss".

The report says:
* US military officials failed to keep proper records on about 87,000 rifles, pistols, mortars and other weapons sent to Afghanistan between December 2004 and June 2008 - about a third of all the weapons sent

* There was a similar lack of management of a further 135,000 light weapons donated to Afghan forces via the US military by 21 countries

* The military failed even to record the serial numbers of some 46,000 weapons, making it impossible to confirm receipt of weapons or identify any which had fallen into the hands of militants

* The serial numbers of 41,000 weapons were recorded, but US military officials still had no idea where they were
"Lapses in accountability occurred throughout the supply chain," concludes the report, which is due to be discussed on Thursday at a panel hearing of a House Oversight and Government Reform subcommittee.

In response, the Pentagon agreed that it needed more people to help train the Afghanistan government to track the weapons, the AP news agency reported.

It said it had made attempts to address the problems with registering serial numbers and monitoring weapon locations.

The report's findings came just a day after an audacious attack on three government buildings in the Afghan capital Kabul left 28 people, including eight attackers, dead.

The report is reminiscent of an August 2007 study, also by the GAO, which found the US military could not account for some 190,000 rifles and pistols given to security services in Iraq.

One of the US lawmakers who will discuss the report findings on Thursday, Democratic Representative John Tierney, suggested the report could prompt Congress to legislate on weapons-handling in Afghanistan.

"The challenges here are immense, but this is just too important not to get it right," he said.