Iceland is the world's most peaceful nation while the United States is ranked among the bottom third, according to a study released on Tuesday.

The "Global Peace Index," compiled by the Economist Intelligence Unit, ranked the United States 97th out of 140 countries according to how peaceful they were domestically and how they interacted with the outside world.

The United States slipped from 96th last year, but was still ahead of foe Iran which ranked 105th. It, however, lagged Belarus, Cuba, South Korea, Chile, Libya and others which were listed as more peaceful.

Iraq, which the United States invaded in 2003, leading to the toppling of Saddam Hussein, ranked lowest on the index. Afghanistan, another country invaded by the United States this decade, was also in the bottom five...