WASHINGTON — The U.S. government knows it's awarded nearly $18 billion in contracts for rebuilding Afghanistan over the last three years, but it can't account for spending before 2007.

Thousands of firms received wartime contracts, but the special inspector general for Afghanistan reconstruction found it too difficult to untangle how billions of additional dollars had been spent because of the U.S. agencies' poor recordkeeping.

"Navigating the confusing labyrinth of government contracting is difficult, at best," the inspector general says in a report that was released Wednesday.

The finding raises doubts about whether the U.S. government ever will determine whether taxpayers' money was spent wisely in Afghanistan.

"Data got better from 2007 on," said Susan Phalen, a spokeswoman with SIGAR, "but it remains to be seen whether we'll ever know how much U.S. agencies spent overall."

Overall, the U.S. has set aside about $55 billion for rebuilding Afghanistan, but that includes agencies' budget for staff salaries, operations and security. SIGAR couldn't parse how much was spent on contractors alone.

SIGAR recommended that the Pentagon, the State Department and the U.S. Agency for International Development create one database to track wartime contracts. As it stands, the Pentagon has four contracting agencies that oversee contracts, but none of them is sharing information. SIGAR found a lack of coordination among all the U.S. agencies that oversee contracting in Afghanistan, not just the Pentagon.

Meanwhile, a handful of companies received a majority of the contracts, auditors found.

USAID, for example, awarded almost half of the $2 billion it set aside for Afghanistan projects to two companies, Louis Berger and Development Alternatives Inc. Overall, the agency doled out contracts to 214 companies.

Of 6,600 firms that have received contracts from the Pentagon for Afghanistan, 44 of them received more than half the military's business there. One contractor, DynCorp International, accounted for about 75 percent of all the contracts for Afghanistan that two State Department bureaus awarded.

The military's joint contracting command acknowledged problems with its tracking, but it told auditors that it's trying to improve it.

Although the State Department and USAID received drafts of the report from SIGAR so they could comment on it, they didn't respond.

The report is the latest to criticize the U.S.'s handling of contracts in Afghanistan. A SIGAR audit released Wednesday concluded that six police stations in a dangerous stretch of southern Afghanistan were so poorly constructed by the Afghan contractor that they can't be occupied. The U.S. Army Corps of Engineers didn't detect the problems and paid the firm almost $5 million of the $5.5 million contract price.

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