The US has spent more than $4 trillion on foreign wars since the 9/11 attacks, a report said Wednesday.

The report by Watson Institute at Brown University said conflicts in Afghanistan, Pakistan, Iraq and Syria have cost $4.3 trillion and could reach $5.6 trillion by the end of 2018.

The total cost for an individual taxpayer over this period was estimated at $23,386, the report said.

A similar report released by the Pentagon puts the cost of the wars at just $1.52 trillion and $7,740 per taxpayer.

The Brown analysis includes other estimates that are not related to the Department of Defense including war-related spending by the State Department, Department of Veterans Affairs and Homeland Security.