In probably his toughest comments yet on the Iranian nuclear issue ahead of his meeting with Israeli Prime Minister Benjamin Netanyahu, Obama made it clear that it was "unacceptable" for Iran to have a nuclear weapon.
"I think that the Israeli government recognises that, as president of the United States, I don't bluff," Obama told The Atlantic magazine in an interview published today.
"I also don't, as a matter of sound policy, go around advertising exactly what our intentions are. But I think both the Iranian and the Israeli governments recognise that when the United States says it is unacceptable for Iran to have a nuclear weapon, we mean what we say," Obama said.
Obama warned against a premature strike on Iran, saying it might inadvertently help the Islamic Republic.
"At a time when there is not a lot of sympathy for Iran and its only real ally (Syria) is on the ropes, do we want a distraction in which suddenly Iran can portray itself as a victim?," he said.
Israel has maintained that all options remain on the table with regard to action on Iran, including a pre-emptive military strike on Iranian nuclear installations.
Obama also rejected as unreasonable a more limited policy of containment in confronting Iran's nuclear efforts.
"You're talking about the most volatile region in the world," he said. "It will not be tolerable to a number of states in that region for Iran to have a nuclear weapon and them not to have a nuclear weapon. Iran is known to sponsor terrorist organisations, so the threat of proliferation becomes that much more severe."He also said that the US and EU sanctions against the Iranian regime are starting to bite.