US-Iranian relations have been stalled for over three decades due to missteps in timing, distrust, hostility and ideological differences between Tehran and Washington. Six American presidents have experimented with different political and economic tools in an effort to reverse Iranian support for terrorist groups, its opposition to Israel and its pursuit of a nuclear programme. President Barack Obama’s direct engagement with Tehran to end the nuclear standoff is a first step towards improved relations between two estranged countries that share a number of mutual interests.