Foreign affairs can have a way of disrupting a president's best-laid plans. President Obama, we suspect, would like nothing better than to focus attention during his second term on domestic policies. Among the factors that will determine his presidential legacy will be how successfully his administration implements the Affordable Care Act, whether the economy sees sustained growth, and reining in deficit spending.

The president referenced his yearning to refocus on the home front during his weekly radio broadcast last May.

"After more than a decade of war, it is time to focus on nation building here at home," he said then.

Yet a look forward to 2013 shows an international scene fraught with disquieting trends and problems that if not dealt with deftly by the State Department could spell bigger trouble and divert attention from "nation building here at home."

Despite the toughest economic sanctions ever employed in peace time, and unprecedented and sustained international cooperation, Iran continues to resist demands that it abandon its pursuit of a nuclear arsenal. The Iran economy is in distress, its currency devalued, its oil sales suffering, yet that nation's theocrats refuse to yield to reason.

Keeping the military option on the table, President Obama has said the United States will not tolerate a nuclear-armed Iran. Yet it is an option the administration should only take when all others fail. The consequences of what would follow an attack on Iran are unpredictable and explosive. For now the best course is keeping up the economic pressure.

Iran is just one component in a volatile Middle East. In Syria, President Bashar Assad's grip on power continues to weaken in a civil war that claimed an estimated 35,000 lives in 2012. But there is reason to believe President Assad's regime could continue for months and become increasingly brutal, and perhaps resort to chemical weapons, as it tries to hang on.

More troubling for the United States is what follows Assad. The United States and key allies have coalesced in support of the relatively moderate Syrian National Coalition. But jihadists, including elements linked to al-Qaida, have proved to be among the fiercest and most effective rebel fighting forces. The potential for a strategically and geographically important Syria to fragment post-Assad is great. To make sure Assad falls and the right people win, the Obama administration may have to get over its reluctance to arm rebel forces.

In Iraq, a weak and ineffective central government directed by Prime Minister Nouri al-Maliki, a leader who was propped up by the United States, is inviting growing independence by the Kurdistan territory in the north. Complicating matters was the decision by neighboring Turkey to begin dealing directly with the Kurds to access Iraqi oil and repair damaged infrastructure. This is another instance in which outcomes are troubling unpredictable should Mr. al-Maliki use military force to assert control over the Kurds.

In Egypt, concern grows that Islamists have seized the revolution, gaining voter approval for a revamped constitution that relegates women, the Coptic Christian minority and those with secular, liberal views to second-class status. The Obama administration must use the threat of reduced U.S. aid to that country to keep President Muhammad Morsi from straying too far from his promise to run a government respectful of all Egyptians. If dissidents cannot use the democratic process to air their grievances, expect more civil unrest.

Those are some of the predictable hot spots, but history shows trouble often comes from unexpected sources. The president made a solid choice in nominating Sen. John Kerry, D-Mass., chairman of the Foreign Relations Committee, as his new Secretary of State. A decorated veteran with extensive foreign policy experience and both political and diplomatic acumen, Sen. Kerry should be an important asset as the administration deals with its foreign policy challenges; perhaps even allowing the president to focus on domestic policy.