US Dilemna: "How to back the rebels enough to induce the regime to negotiate but not enough to trigger a regime collapse"

"... If the jihadis manage to retain their vanguard position in a new Syria, it is not hard to imagine the emergence of an informal - possibly even formal - union between Sunni parts of western Iraq and a Sunni-dominated Syria, as the region slides into a kind of sectarian and ethnic balkanisation whose fault-lines are already visible.Which is one reason why the Americans and their allies are reluctant to push too hard in the other proxy struggle they are waging in Syria - against Iran and its allies, Hezbollah and the Damascus regime itself.
The survival of the Assad regime, or its transition into something retaining many of its pluralistic traits and structures, is the only serious obstacle to that process.
The dilemma the Americans face - and which they will be trying to resolve in a series of meetings between President Barack Obama and Middle East allies in the coming weeks - is how to back the rebels enough to induce the stubborn regime to negotiate a controlled transition, but not enough to trigger an abrupt regime collapse which might allow the radicals to take over...."