BEIRUT – Not long ago, Arabs everywhere listened when the leader of Hezbollah spoke. Sheik Hassan Nasrallah's prominence, bolstered by his Lebanese guerrilla force's battles against Israel, was a sign of the rising regional influence of Shiite Muslims and overwhelmingly Shiite Iran. Now, his speeches don't necessarily make front pages even in Lebanon.

The change is emblematic of how the bloody conflict in Syria, now in its 18th month, has brought a shift in the Middle East's sectarian power balance. For much of the past few years, Shiites were surging in power across the region, based on the central alliance between Iran, Syria and Hezbollah, with close relations to Shiites who took power in post-Saddam Hussein Iraq.

But now the region's Sunni-led powers are appearing more confident, encouraged by the prospect that the Sunni-led rebellion could bring down Syrian President Bashar Assad's regime, dominated by members of the Shiite offshoot sect of Alawites. Assad's fall would cost Iran a priceless foothold in the heart of the Arab world. Hezbollah would lose a bastion of support and a conduit via Syria for vital Iranian weapon supplies.