A Republican Senator has sparked outrage at an international security conference after saying the U.S. should be prepared to launch a military attack on Iran to 'neuter' its hard-line regime.

Lindsey Graham, who represents South Carolina, told surprised attendees at the Halifax International Security Forum that an attack could cripple Iran's nuclear programme and armed forces.

He said that although international sanctions were beginning to work, President Barack Obama should make it 'abundantly clear' that 'all options are on the table'.