Iran appears to be years away from possessing nuclear weapons, giving time for diplomacy to work, Barr said in a release. He said that war with Iran would be a disaster.

"American troops in Iraq would be at risk. U.S. citizens would be targeted for terrorist acts," he said. "Tehran could retaliate against Israel. Oil shipments would be disrupted, causing energy prices to soar even higher. Allied states in the Persian Gulf would be vulnerable to attack. Chances for democratic change in Iran would be set back."

A former Republican, Barr represented Georgia in Congress from 1995 to 2003, serving on the House Judiciary Committee and was known for his commitment to civil liberties.

Barr became a critic of the Bush administration when he left Congress and endorsed the Libertarian candidate for president in 2004.