The war against the Islamic State in Iraq and Syria (ISIS) could cost the United States between $2.4 billion and $22 billion per year, according a report released Monday by a nonpartisan Washington-based budget research institute.

The Center for Strategic and Budgetary Assessments (CSBA), which evaluates spending on national security, estimates the cost of U.S. operations against ISIS since mid-June is likely between $780 million and $930 million — less than 0.2 percent of the Pentagon’s fiscal 2014 budget.

“The cost of future operations depends primarily on how operations continue, the intensity of air operations, and whether additional ground forces are deployed beyond what is already planned,” CSBA’s report said.

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If air operations continue at a moderate level and 2,000 ground forces are deployed in total, the organization predicts operations could cost between $200 and $320 million per month.

President Obama has so far authorized deployment of 1,600 U.S. personnel to Iraq to assist the country's security forces and protect diplomatic facilities.

The CSBA, however, said, if air operations are increased to a higher pace and 5,000 ground forces are deployed, the U.S. could pay between $350 million and $570 million per month.

If air operations are expanded significantly and 25,000 U.S. troops are put on the ground, the price tag could reach $1.1 to $1.8 billion per month, the CSBA said. In such a scenario, the report said roughly 80 percent of the cost of the war would be based on the ground presence.

“On an annualized basis, the lower-intensity air operations could cost $2.4 to $3.8 billion per year, the higher-intensity air operations could cost $4.2 to $6.8 billion per year, and deployment of a larger ground contingent could drive annual costs as high as $13 to $22 billion,” the group predicted.

The higher costs, however, are nowhere near as high as the peak costs in Iraq and Afghanistan, which peaked at $164 billion in 2008 and $122 billion in 2011, respectively.

The CSBA said its estimates are based on publicly available information on types of aircraft and munitions used, bases available to U.S. forces and spending on previous military operations.

The estimates, however, do not cover the costs of humanitarian relief, weapons supplied to partner forces, the training of those forces, contributions to air and ground operations from allies and covert operations.

On Thursday, the Pentagon said costs of U.S. efforts against ISIS are estimated to be $7 million to $10 million per day, up from the $7.5 million per day in late August.

Nearly a week ago, the Obama administration expanded airstrikes to Syria, in addition to those launched in Iraq.