The United States has spent or will have spent nearly $6 trillion on its war on terrorism since it began in 2001, a new study showed Wednesday, according to UPI.com.

The "Costs of War Project" by the Watson Institute of International and Public Affairs at Brown University charted the hidden and unacknowledged costs of use of military force against terrorism.

The 35-member staff of scholars, legal experts, human rights activists and physicians included the cost of expected future obligations -- like ongoing care for veterans -- into their calculations. The U.S. political landscape, the status of women in war zones and the transparency of governments in Iraq and Afghanistan were also considered.

A 13-page summary of the analysis said $5.9 trillion has been spent or promised -- and that figure will rise to $7 trillion if present military conflicts continue into the 2020s.

The institute's reported cost is several times higher than official Defense Department estimates, largely because the study included hikes in Homeland Security and Veterans Affairs spending and costs of military equipment and personnel.

"Because the nation has tended to focus its attention only on direct military spending, we have often discounted the larger budgetary costs of the post-9/11 wars, and therefore underestimated their greater budgetary and economic significance," the report states.

The institute adds that appropriations for the wars in Iraq and Afghanistan were financed by interest-accruing deficit spending and borrowing instead of new taxes.

Wednesday's study said the Pentagon budget has grown by more than $900 billion over the last 17 years, because of "increased missions, recruiting costs and service member benefits."