President Obama, speaking to ABC in an interview taped Friday and broadcast Sunday, confirmed that he and Iran’s new President Hassan Rouhani have exchanged letters, and said he holds out hope that the US and Iran can reach a nuclear deal. But he said that negotiating with Iran would not be easy, and stressed that Iran should not doubt his resolve to prevent it getting nuclear weapons, despite the US agreeing to a last-minute Russian bid to remove Syria’s chemical weapons to avoid possible US-led air strikes.

“I have. And he’s reached out to me,” Obama said, when asked by ABC’s George Stephanopoulos if he’d reached out to the new Iranian president.

“I think what the Iranians understand is that the nuclear issue is a far larger issue for us than the chemical weapons issue,” Obama said, citing the risks to US “core interests” that a nuclear armed Iran would pose to Israel, and of a nuclear arms race in the region.

“My suspicion is that the Iranians recognize they shouldn’t draw a lesson that we haven’t struck [Syria] to think we won’t strike Iran,” Obama said. “On the other hand, what…they should draw from this lesson is that there is the potential of resolving these issues diplomatically.”