>WASHINGTON -- The main Syrian opposition bloc, the Syrian National Council, voted Monday at a meeting in Doha, Qatar, to broaden its ranks in the face of U.S. pressure to create a more representative leadership.

Still, Syria will remain a foreign policy challenge for the U.S., no matter who wins Tuesday's presidential election.

Even as the United States tries to identify the right people for a transitional authority to replace Syrian President Bashar al-Assad, the Obama administration said it is still considering a no-fly zone for northern Syria, but not a military intervention.

Former U.S. Ambassador Frank Wisner said there remains no support for military involvement in Syria from the United States or its allies.

"What we should be talking about is not a military option but a political option, and that option must mean the assumption that as dreadful as this regime is in Syria, as ghastly as the crimes that is committing, you need a political way out of the situation, you need in short a political settlement,” said Wisner.

Some analysts say that the longer the 20-month-old conflict drags on, however, military intervention will be inevitable.

Princeton professor Anne Marie Slaughter, a former U.S. State Department policy planner, says, “I think the U.S. should be doing everything we possibly can at this point to help establish buffer zones, even if that means that they have to be no-fly zones so you have to actually put in planes to protect them."

Some, like Kurt Volker of Arizona State University’s McCain Institute for International Leadership and a former U.S. ambassador to NATO, say the U.S. should build a broader diplomatic base of support along with some military component.

“That would be a combination of no-fly zone, of taking out air defenses, of limiting the ability to use armor inside Syria.  Doing that would give some time and some space to the rebels in Syria, and then what’s already beginning to happen is the development of something of a safe haven on the border with Turkey,” said Volker.

With more than 100,000 Syrian refugees in Turkey, Washington is weighing a no-fly zone for areas of northern Syria controlled by Assad opponents and rebels. But Wisner said no-fly zones are military interventions by a different name.

“A no-fly zone, a humanitarian zone means you have to put troops on the ground. A no-fly zone means you are fighting a war and you are going to have pilots shot down. You will be dragged to military engagement,” said Wisner.

And Wisner said U.S. national interest argues clearly against an American military engagement in the Middle East.

“I hope we have come to a recognition that we can’t have our way with military force, that we have got to use military force in the future in the most sparing manner, when our most vital, direct and essential national interests, ones that affect our immediate security are at stake,” he said.

So far, the U.S. and its allies have preferred to shore up the political arm of Syria's opposition.