Aside from Gaza, Barack Obama's next foreign policy crisis after taking office may be Iran and its nuclear program. Iran is well down the path of being able to enrich uranium on a large enough scale to produce a nuclear weapon. The International Atomic Energy Agency recently reported that Iran may reach this point this year.
An Iran with the ability to produce one or more bombs poses a true danger. One path for the new American administration would be to adopt the "North Korea" option and live with the threat. But this risks making an unstable and conflict-prone Middle East even more so.
In a crisis, Israel or Iran may be tempted to use nuclear weapons out of fear the other might do the same. There is also the chance other countries such as Egypt or Saudi Arabia may develop or acquire nuclear weapons. The United States could reduce these risks by providing missile defence and security guarantees to selective countries, but it is far from clear it would succeed.
Moreover, nuclear proliferation is not the only danger if Iran proceeds with its nuclear efforts. What Iran does directly and through such groups as Hezbollah and Hamas will continue to have a major and mostly adverse effect on the future of Iraq, Afghanistan, Lebanon and Palestine. Iran is one of the Middle East's most powerful countries. A nuclear Iran would probably act more aggressively, believing its nuclear capability afforded it considerable protection.