The Pentagon does a poor job tracking shoulder-fired missiles (search) that the United States sells around the world, making it more difficult to keep the weapons from terrorists, according to a congressional report released Thursday.

There are as many as 750,000 of the light but lethal weapons made by 30 countries, with about 1 percent of the total outside government controls, the General Accounting Office (search) said.

"The proliferation of man-portable air defense systems [MANPADS] has been of growing concern to the United States and other governments," said the investigative arm of Congress.

Terrorists are attracted to the weapons as a way to bring down commercial airliners because the weapons are deadly, portable, easy to use, easy to hide and cost from less than $1,000 each to $100,000, the report said.

Among the missiles are U.S.-made Stingers. Countries that buy Stinger missiles (search) must allow the Defense Department to inspect them.

But, the report said, the Defense Department's Stinger records are "neither complete nor reliable. As a result, DOD cannot account for each Stinger sold abroad."

The problem is not new. In September 1994, the GAO said that the Pentagon's oversight and record-keeping of the weapons was poor. Investigators recommended changes then.

In the report released Thursday, the GAO said that the defense secretary should standardize requirements for keeping Stinger records, create an electronic database to consolidate records of the systems and establish standard procedures for inspecting them.

The Pentagon, in response to the report, said it has a "high level of confidence" that the missiles sold to other nations do not pose a terrorist threat because many different organizations review each proposed transfer.

The Pentagon also said that official procedures for counting and inspecting the missiles would be in place at year's end.

Since the 1970s, more than 40 aircraft have been struck by shoulder-fired missiles, which seek the engine's heat. Of those, 24 crashed and 600 people died.

But it was the first attack outside a conflict area — an unsuccessful attempt on an Israeli charter jet taking off from Mombasa, Kenya, in 2002 — that raised the government's concern about the risk posed by the missiles.

In 2003, the State Department reached agreements with other countries to better control the weapons, but such agreements are voluntary and nonbinding, the report said.

The GAO recommended that the secretary of state work with other countries to figure out ways to monitor how well they are reducing the supply of the weapons and assess whether such efforts dry up the flow to illicit arms markets.

The State Department agreed with the report's recommendations and said that it is working with other countries.

The department has also worked with foreign governments to destroy more than 8,155 excess shoulder-fired missiles and tighten security where they are stored. By March, commitments from nine countries — including Bosnia and Herzegovina, Cambodia, Liberia, Nicaragua and Serbia to destroy nearly 10,000 excess missiles, the report said.