Not only is the Obama administration no longer convinced that Syria's armed rebellion is about to topple President Bashar Al Assad, a rebel military victory does not even appear to be Washington's preferred outcome.
A little over a year ago, then-Secretary of State Hillary Clinton described the Assad regime as "a dead man walking", and President Barack Obama expressed confidence, in his 2012 State of the Union address, that "the Assad regime will soon discover that the forces of change can't be reversed".
This year, by contrast, Syria barely rated a mention in the same speech, with Mr Obama vowing only to "keep the pressure on the Syrian regime ... and support opposition leaders that respect the rights of every Syrian".
The rebels clearly can't win the war with the current level of support being offered by outside powers. Moreover, Mr Obama has reportedly dismissed proposals from within in his administration for arming insurgents, and Monday's European Union rebuff of efforts by the UK, France and Italy to lift an embargo on arming the rebels reinforced the sense of western reluctance to invest in a rebel military victory.
The policy logic underlying these decisions was articulated on Sunday by new Secretary of State John Kerry, who said his goal in Syria was "to see us have a negotiated outcome and minimise the violence". He admitted that achieving that goal remained exceedingly difficult, but insisted that it was in the best interests of "the Syrian people, and the region and the world, to make every effort to explore ways to achieve that negotiated outcome".
Pursuing a military solution, Mr Kerry warned, risked the "implosion" of the Syrian state, with far greater regional risks.
Two years into the rebellion, Syria's civil war remains locked in a strategic stalemate, reports of a renewed rebel offensive notwithstanding. The slow but steady erosion of the regime's grip on much of the countryside underscores the fact that the rebellion has become an irreversible political-military fact, but its failure to capture a single major population centre suggests the regime's better-equipped forces have lost neither the will nor the ability to fight.
Western powers want Mr Al Assad out, but not to be replaced by those leading the armed rebellion, many of who are hostile to US regional interests. Many of the rebels' most impressive tactical gains are being recorded by jihadists such as the Jabhat Al Nusra group, branded by the US as an "international terrorist organisation" and Al Qaeda affiliate.
Even Moaz Al Khatib, leader of the western-backed Syrian National Coalition, rejected the "terrorist" designation and emphasised that the group's involvement was "essential for victory" over Mr Al Assad.
But with the political influence on the ground of Mr Al Khatib's organisation unproven, the US appears in no hurry to pursue the military victory of which he speaks. And the Obama administration has recognised that the factors maintaining the regime - its security forces have not collapsed precisely because most of the Alawites and other key minorities see the rebellion as mortal threat to themselves - are unlikely to change any time soon.
Even if the regime were dislodged from Damascus, that would be unlikely to end a civil war that threatens the survival of the Syrian state.
Given the parameters of the conflict, expanding the armaments available to the rebels is unlikely to end the fighting. And continuing the civil war, many in Washington warn, will keep Syria on the path to failed statehood and even a wider war that draws in all of the region's key stakeholders - a nightmare scenario Mr Obama is desperate to avoid, despite the pressure from critics at home to "do something" in the face of the relentless slaughter in Syria.
The Syrian tragedy has been compounded, all along, by the extent to which the conflict has become hitched to global strategic rivalries, and in particular to the one between Iran and its fiercest Arab adversaries.
Some of those strategic agendas can be pursued without actually delivering the knockout blow: the Syrian regime's allies can be bloodied and distracted by the proxy war, even if its outcome is not decisive. Indeed, US officials allege that Iran has trained and organised Alawite militias to ensure the country remains ungovernable for its foes even if the Assad regime is unable to hold on to Damascus.
Despite signs of growing international pressure on both sides for talks, no compromise agreement appears imminent. The Assad regime has rejected a Russian-brokered meeting with the western-backed Syrian National Coalition, while the coalition has reverted to demanding Mr Al Assad's ouster as a condition for talks.
The coalition leader, Mr Al Khatib, drew praise from the US when he suggested at a security conference in Munich three weeks ago that he would be prepared to negotiate with regime representatives if political prisoners were freed - an offer roundly denounced by his own organisation. A Syrian minister last week offered to meet the SNC chief in any foreign city, but that, too, was quickly retracted.
Even as the rebels make new tactical gains on the ground - downing two regime aircraft, capturing an oil town and the Al Furat hydroelectric dam in the north-east, and an airbase in the north, as well as launching a new offensive in the suburbs of Damascus - a substantial shift in the strategic balance does not appear forthcoming.
The response of both the regime and the opposition to ongoing negotiation efforts appears guided by the belief that they can win the war. This despite emerging signs that key backers of both sides have begun to recognise that neither side is capable of defeating the other.
So the Obama administration's reticence to this point may be guided by a recognition that while neither the regime nor the rebels is capable of destroying the other, in combination they are more than capable of destroying Syria - and may even have already done so.
Tony Karon is an analyst based in New York
On Twitter: @TonyKaron