The U.S. war in Iraq has cost $1.7 trillion with an additional $490 billion in benefits owed to war veterans, expenses that could grow to more than $6 trillion over the next four decades counting interest, a study released on Thursday said.

The war has killed at least 134,000 Iraqi civilians and may have contributed to the deaths of as many as four times that number, according to the Costs of War Project by the Watson Institute for International Studies at Brown University.

When security forces, insurgents, journalists and humanitarian workers were included, the war’s death toll rose to an estimated 176,000 to 189,000, the study said.