A “surge” of U.S. civilian officials into Afghanistan has cost about $1.7 billion since 2009, and is likely to get a lot more expensive soon, according to a new audit.

Two years ago, the Obama administration announced plans to send hundreds of more civilians to Afghanistan, with hopes that diplomats, specialists from across the U.S. government and others could help improve Afghan governance and encourage sustainable economic growth. The administration has said the initiative has yielded significant benefits, even as lawmakers have questioned whether the money spent has accomplished much.

The new audit, from the State Department’s inspector general and the Special Inspector General for Afghanistan Reconstruction, does not address the initiative’s effectiveness. But it does say that, with budget pressures increasing in Washington, civilian efforts in Afghanistan face significant challenges going forward.

Among the reasons: with the U.S. military drawing down, some security functions will likely be picked up by the State Department; two new consulates are being opened, increasing costs; and some lawmakers are proposing standardizing pay and benefits for all civilians in Afghanistan, which would also increase costs.

All of which means that, with 1,040 civilian personnel deployed as of June, the surge faces a very uncertain future. Already, it costs the U.S. government between $410,000 and $570,000 to employ each civilian employee in Afghanistan over the course of the year.

That’s less than the estimated $694,000 it cost to keep a service member in Afghanistan this year, and there are about 100 times more troops in country than civilians. What’s more, the overall cost of the U.S. civilian effort is a pittance when compared with the costs of the military campaign.

Still, at a time of fiscal pressure, the $1.7 billion risks looking like a big chunk of change to lawmakers.

“The economic burdens currently challenging the U.S. reinforce the need to ensure that every American taxpayer dollar spent in Afghanistan goes toward development projects that are necessary, sustainable and achievable,” Sen. Benjamin Cardin (D-Md.) said in a statement Thursday. “I look forward to working with the State Department and USAID to make sure that the American taxpayers dollars are spent wisely and with ever greater accountability.”

State Department officials, in a letter included in the audit, asserted that it was misleading to say the surge had cost $1.7 billion, and that the cost of keeping additional civilians to Afghanistan over three years was closer to $1.2 billion if the figure includes only costs related to the growth of the civilian force, and not fixed costs such as housing and offices.

As for the audit’s conclusion that there are challenges ahead, the officials concurred, but suggested the State Department is taking steps to address funding concerns.