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President Obama has exchanged letters with Iranian president

15 September 2013 Last updated at 17:11 BST

In an exclusive interview with ABC's This Week, President Obama has spoken about the implications of the Syria chemical weapons agreement and the implications this has with Iran.

He said: "My suspicion is that the Iranians recognise that they shouldn't draw a lesson that we haven't struck [Syria] to think we won't strike Iran."

The US president said: "What the Iranians understand is that the nuclear issue is far larger for us than the chemical weapons issue".