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.
Obama also warned that if Iran gets nuclear weapons, then four or five countries would start a nuclear weapons program in the region that would increase the prospect of miscalculation five-ten folds that a India-Pakistan one.
"Absolutely," Obama said when asked if he sees accidental nuclear escalation as an issue.
"Look, the fact is, I don`t think any of it would be accidental. I think it would be very intentional," he said.
"If Iran gets a nuclear weapon, I won`t name the countries, but there are probably four or five countries in the Middle East who say, `We are going to start a program, and we will have nuclear weapons.` And at that point, the prospect for miscalculation in a region that has that many tensions and fissures is profound. You essentially then duplicate the challenges of India and Pakistan fivefold or tenfold."
"The risks of an Iranian nuclear weapon falling into the hands of terrorist organizations are profound. It is almost certain that other players in the region would feel it necessary to get their own nuclear weapons. So now you have the prospect of a nuclear arms race in the most volatile region in the world, one that is rife with unstable governments and sectarian tensions," he said.
"And it would also provide Iran the additional capability to sponsor and protect its proxies in carrying out terrorist attacks, because they are less fearful of retaliation," he said.