An eruption of violent unrest across the Middle East is confronting President Barack Obama with the most serious challenge yet to his efforts to keep the Arab Spring from morphing into a new wave of anti-Americanism - and he has few good options to prevent it.

The Obama administration was caught flat-footed by a wave of pro-democracy revolts last year that toppled autocratic leaders - some, like Egypt's Hosni Mubarak, a longtime U.S. ally. But Washington gradually gave cautious backing to the goals of the Arab Spring movement.

Now, with much of the U.S. optimism that accompanied the Arab world's uprisings seemingly gone for good, Washington faces an apparent rise in Islamic activism and declining influence over countries it once counted as allies.