According to the institute's report, the United States spent $610 billion on its military last year, almost three times more than the second-biggest spender, China, who is estimated to have spent $216 billion. Russia's defense spending is estimated at $84.5 billion.
"US military spending continues to run at historically high levels and is around the same level in real terms as at its previous peak in the late 1980s," the Institute said.
In 2014, the United States accounted for 34 percent of all military spending in the world.
Despite such high levels of spending, US Senator Tom Cotton said that the country's defense budget had fallen to a historic low that reflects a policy of "retreat." Only 16 percent of all federal spending goes towards defense, Cotton said.