The U.S. government's new war in Iraq that now also includes Syria has already cost American taxpayers between $780 and $930 million, and could amount to over $1 billion a month if U.S. efforts intensify on the scale demanded by war hawks in Congress, according to a think tank analysis published this week.

According to the Center for Strategic and Budgetary Assessments:

Assuming a moderate level of air operations and 2,000 deployed ground forces, the costs would likely run between $200 and $320 million per month. If air operations are conducted at a higher pace and 5,000 ground forces are deployed, the costs would be between $350 and $570 million per month. If operations expand significantly to include the deployment of 25,000 U.S. troops on the ground, as some have recommended, costs would likely reach $1.1 to $1.8 billion per month.

On an annual basis, CSBA estimates, the U.S. military's operation against the Islamic State in Iraq and Syria (or ISIS) could cost as much as $22 billion dollars a year.

The Pentagon is currently funding the attack through a controversial war fund, dubbed the Overseas Contingency Operations account, which is exempt from federal budget caps. The fund was originally created to fund the previous wars in Iraq and Afghanistan though defense officials say it will likely be around for the "long-term."

CSBA notes that the range in estimates highlights "the high degree of uncertainty involved in current operations." One source of uncertainty, the group writes, "are the desired end states in both Iraq and Syria—i.e. what the United States would like to leave in place if and when ISIL is destroyed."

The National Priorities Project (NPP) last month issued an estimate that the military action against ISIS had already cost U.S. taxpayers $312,500 per hour and, according to their running tally, has cost over $804 million.

In a statement issued following President Obama's announcement of the escalated bombing campaign, NPP wrote that U.S. leadership would be wise to "look to our past involvement in the region" before plunging American taxpayers into another costly and endless war.

In 2003, President Bush said his purported goal of bringing democracy to Iraq would require a "lengthy campaign" and cost and estimated $60 billion, which NPP notes is just a "small fraction" of their $817 billion estimate. (Economist Joseph Stiglitz even argues that the cost of the wars in Iraq and Afghanistan could amount to as much as $4 trillion.)

As NPP writes, continued U.S. involvement in the region "has instead further muddied and even exacerbated centuries-old ethnic and religious divisions, while providing an endless supply of fodder to fuel the flames of extremist terrorist groups like al-Qaeda and ISIS."

NPP, which has spent over thirty years tracking the cost of war, adds that in exchange for the conflict, our nation has sacrificed lives as well as "our own social and economic potential, as we sunk over a trillion dollars into war while investing less in our domestic needs (such as addressing our crumbling infrastructure, revitalizing the job market, or reducing the burden of student loan debt)."

The irony, as Middle East scholar Juan Cole points out on Tuesday, is that the costly drums of war are being beaten by the same Congress that in February slashed $8.7 billion from federal food stamp funding.

Cole writes: "[T]he same people who have trouble justifying a safety net for the working poor and find it urgent to cut billions from the programs that keep us a civilized society rather than a predatory jungle—the same people have no difficulty authorizing billions for vague bombing campaigns that are unlikely to be successful on any genuine metric."

According to U.S. Central Command, U.S. air strikes in Iraq and Syria continued Monday and Tuesday with "attack, fighter and remotely piloted aircraft" conducting 11 strikes in each country.

The CSBA report uses the term "ground forces" to refer to any U.S. military personnel deployed on the ground, whether in a combat or logistical capacity. The highest estimate assumes a scenario in which combat troops are deployed to both Iraq and Syria. President Obama has repeatedly pledged that there will be "no U.S. combat troops on the ground" in Iraq. However, at least 1,600 U.S. troops that have been deployed since U.S. strikes began on August 8.