A reconstruction program in Afghanistan has spent less than its annual budget for six years straight, but that hasn't stopped the Department of Defense from requesting hundreds of millions more each year.

The Commanders Emergency Response Program provides money for small-scale humanitarian and reconstruction projects that immediately assist local populations. Last year, it used only a fraction of its $200 million budget.

But DOD still requested $60 million for the program for 2014, according to the Special Inspector General for Afghanistan Reconstruction. Congress denied the request, appropriating $30 million to match the decreasing demand.

The program has received between $200 million and $1 billion each year since 2008, according to SIGAR. Some years, less than half the budget was obligated toward projects, but the money kept on coming.

Between 2008 and 2013, CERP commanders spent less than budgeted and kept getting more than necessary for the next year, according to a letter Special Inspector General John F. Sopko sent to military officials Wednesday.

He sent the letter to Marine Gen. Joseph Dunford, commander of U.S. forces in Afghanistan and the International Security Assistance Force, along with Undersecretary of Defense Robert F. Hale and Secretary of the Army John McHugh.

"The Department of Defense (DOD) only obligated $43.5 million of $200 million appropriated for CERP before the funds expired at the end of September 2013," Sopko wrote. "This is not a new phenomenon. ... [O]ver the past six fiscal years the DOD has used only 59 percent of the CERP funds provided by Congress."

There are several reasons the money wasn't spent, Sopko said: the troop drawdown in Afghanistsan, effective oversight that cut project costs and the unpredictable nature of planning projects in a war zone.

But more important than why it wasn't spent is what happened to that money, Sopko wrote. He asked the commanders to explain why the money wasn't spent; whether the money was used for another purpose or returned to the Treasury; and why DOD kept requesting more money than program officials needed.

Sopko also requested detailed information on program spending and oversight, and a list of all CERP projects.

Contractors aren't the only ones requesting money they'll never use. Defense contractors secured billions of dollars in the Defense Department's budget this year for projects DOD doesn't even plan to complete, the Washington Examiner reported Thursday.