"What I have said is that it is in the world's interests for Iran to set aside ambitions for a nuclear weapon," he said, and the best way for that to be accomplished was "through tough direct diplomacy".
"Although I don't want to put artificial timetables on that process, we do want to make sure that, by the end of this year, we've actually seen a serious process move forward".
Mr Obama is due to arrive in Saudi Arabia on Wednesday on the first stage of his tour of the Middle East and Europe.
He will travel to Egypt on 4 June, where he is set to give a key speech on US ties with the region, before carrying on to Europe to attend D-Day commemoration events.
The president has faced criticism over his decision to give a speech in Cairo, with human rights groups pointing to Egypt's patchy reputation for political freedom.
But he said while there were "obviously" human rights issues to address in some Middle Eastern countries, the job of the US was not to lecture but to encourage what he said were "universal principles" that those countries could "embrace and affirm as part of their national identity".
"The danger, I think, is when the United States, or any country, thinks that we can simply impose these values on another country with a different history and a different culture," he said.
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