WASHINGTON — The Pentagon plans to destroy more than $1 billion worth of ammunition although some of those bullets and missiles could still be used by troops, according to the Pentagon and congressional sources.

It’s impossible to know what portion of the arsenal slated for destruction — valued at $1.2 billion by the Pentagon — remains viable because the Defense Department’s inventory systems can’t share data effectively, according to a Government Accountability Office report obtained by USA TODAY.

The result: potential waste of unknown value.

“There is a huge opportunity to save millions, if not billions of dollars if the (Pentagon) can make some common-sense improvements to how it manages ammunition,” said Sen. Tom Carper, D-Del., and chairman of the Homeland Security and Governmental Affairs Committee. “Despite years of effort, the Army, Navy and Air Force still don’t have an efficient process for doing something as basic as sharing excess bullets. This Government Accountability Office (GAO) report clearly shows that our military’s antiquated systems lead to millions of dollars in wasteful ammunition purchases.”

The Army and Pentagon, in a statement, acknowledged “the need to automate the process” and will make it a priority in future budgets. In all, the Pentagon manages a stockpile of conventional ammunition worth $70 billion.

The effect of inaccurate accounting of ammunition for troops at war was outside the scope of the study. However, there were limited supplies at times of .50-caliber machine gun and 9mm handgun ammunition at the height of the wars in Iraq and Afghanistan, according to a senior military officer who spoke on condition of anonymity to talk about the issue.

“We simply cannot afford this type of waste and ineffectiveness,” Carper said. “The (Pentagon) has a responsibility to efficiently manage its ammunition stocks, not only because it is important to be fiscally responsible, but also because our antiquated ammunition inventory systems can shortchange our war fighters and compromise their ability to complete their mission.”

Other key findings from the report:

• The services have inventory systems for ammunition that cannot share data directly despite working for decades to develop a single database. Only the Army uses the standard Pentagon format; “the Air Force, Navy and Marine Corps operate with formats that are obsolete.”

• The services hold an annual conference to share information about surplus ammunition and swap bullets and other munitions as needed. Data about ammunition left over after the meeting disappears from the books, resulting in an unknown amount of good bullets headed to the scrap heap.

• The Army, although required by regulation, had not reported annually on its missile stockpile until last month, shortly before the GAO study was to be released.

The report illustrates the obsolete nature of the Pentagon’s inventory systems for ammunition. A request for ammunition from the Marine Corps, for example, is e-mailed to the Army. The e-mail is printed out and manually retyped into the Army system because the services cannot share data directly. Not only is this time consuming, but it can introduce errors — by an incorrect keystroke, for example.

Waste, buying new ammunition while usable stockpiles exist, can occur “because the Army does not report information on all available and usable items,” the report states. The annual conference among the services — although it saves about $70 million per year, according to the Pentagon — is inadequate. The services, in fiscal year 2012, exchanged 44 million items, including 32 million bullets for machine guns and pistols.

“Specifically, the Army’s report does not include information from prior years about usable ammunition that was unclaimed by another service and stored for potential foreign military sales or slated for potential disposal,” the report says.

Missiles are another source for concern, the report notes. The Army has an inventory of missiles, including Stingers, Javelins and Hellfires, that has totaled more than $14 billion in recent years. Hellfire missiles have been a weapon of choice for the wars in Iraq and Afghanistan, and in the CIA-run Predator and Reaper drone missions to kill terrorists in places like Yemen.

The GAO found that the Army and its missile command “do not contribute to required annual report.” The reason, Army officials told investigators, is that it “rarely has items to offer for redistribution.”

Without its cooperation, the Army “risks others services spending additional funds to procure missiles that are already unused and usable in the Army’s stockpile.”

The Army, in a statement, said that it began offering that information to the other services last month.

In its recommendations, the GAO urged Defense Secretary Chuck Hagel to require the Army to make known information on all available for use by all services.