Indeed, much tougher sanctions than the previous, ostensibly more "hawkish" Bush administration was ever able to accomplish. Israel and other partners should trust that he is willing to use all elements of national power to prevent Iran from developing nuclear weapons because he is already doing it. Sanctions, diplomatic efforts to isolate the Iranian regime, and intelligence activities have all been used and integrated toward that objective.
And, on the military front, when Obama says all options are on the table, he has actually backed that with concrete actions. Even as U.S. forces completed their drawdown from Iraq, he authorized the re-posturing of U.S. forces in the Gulf to ensure they were set to deal with any scenario, defend our partners, and check Iranian aggression in the region. He deployed a second aircraft carrier, improved U.S. air and missile defenses in the region, bolstered the defensive capabilities of Gulf states (including a record-setting arms package to the Saudis), and done more than any previous administration, in terms of security assistance and defense cooperation, for Israel's security. Moreover, Gen. Martin Dempsey, the current Chairman of the Joint Chiefs of Staff, has noted on more than one occasion that the United States military is prepared and has a viable plan for any Iran contingency, and Secretary Panetta and others have pointed to the unique capabilities the United States military has developed--most notably the Massive Ordinance Penetrator--to ensure the maximum prospects for success should they be called upon. So, when Obama says "all options are on the table," these aren't just words -- the options are viable and the table has been set.
Third, Obama recognizes the threat a nuclear-armed Iran would pose to Israel's security and to the stability of a region that is absolutely vital to U.S. interests. He also believes that if Iran is allowed to cross the nuclear threshold it would do grave damage to the non-proliferation regime -- an issue that he cares passionately about. Because, in Obama's view, it is a vital U.S. interest to prevent Iran from acquiring nuclear weapons, one does not have to trust that he will take all necessary actions for Israel's sake -- one only has to trust that he will act in the U.S. national interest. He would clearly prefer not to use force -- and has cautioned against cavalier and "loose" talk of war given the costs and uncertainties.
But Obama has shown, repeatedly, that he is willing to use force in the U.S. national interest -- whether unilaterally or as part of a multilateral coalition. Don't take my word on that front -- just ask Osama Bin Laden or Muammar Gaddafi. Again, Obama clearly prefers a diplomatic solution, but no one should question the man's mettle on issues like this.
Finally, I think the intelligence picture, the level of inspections, and the international focus is much greater in the case of Iran than was the case with either Pakistan or North Korea. As such, I think it is much less likely that Iran could slip across the nuclear threshold without us knowing about it in time to act. At the moment, for example, it would take at least four months for the Iranians to enrich to weapons-grade level, and they would have to do it at declared facilities -- so they would get caught. Moreover, Western intelligence services have a pretty good track record of uncovering Iranian covert nuclear activities (e.g., Natanz and Fordow). I don't mean to be sanguine about the intel picture -- it is clearly imperfect and our assessments are fallible. But we are in a much better position to detect an Iranian break-out in time to act than was the case with other examples -- and, importantly, we are already focusing all elements of national power on the issue so we are poised and capable of responding quickly in the event that the Iranians are foolish enough to try to dash to a bomb anytime soon.