US President Barack Obama says Iran should draw "a lesson" from the deal reached over Syria's chemical weapons, BBC reported.
Iran's nuclear programme is a "far larger issue" for the US than chemical weapons, Mr Obama told the ABC network.
Mr Obama said despite the fact that the US had not used force against Syria, a "credible threat of force" could lead to a deal.
Mr Obama also confirmed that he had exchanged letters with new Iranian President Hassan Rouhani.
Although the fact that the two leaders have communicated at all will be seen as a step forward, Mr Obama said: "I think this new president is not going to suddenly make it easy."
Mr Obama was referring to the dispute over Iran's nuclear programme, which Western countries suspect is aimed at acquiring a nuclear weapon.
Iran denies this and says the programme's aims are purely peaceful.
Mr Obama said in the ABC interview that Iran should not take comfort from the fact that the US had not taken military action in Syria.
"What they should draw from this lesson is that there is the potential of resolving these issues diplomatically," Mr Obama said.
"If you have both a credible threat of force, combined with a rigorous diplomatic effort... you can strike a deal," he went on.
Mr Rouhani is seen as trying to build a more conciliatory foreign policy than his predecessor Mahmoud Ahmadinejad.
Earlier this month Mr Rouhani transferred responsibility for talks on the country's nuclear programme to the foreign ministry.
Until now they had been conducted by the Supreme National Security Council, which is appointed by and answerable to the Supreme Leader, Ayatollah Khamenei.
Correspondents said the move could herald a less hardline stance in future talks.