The threat from Islamic State fighters to the Syrian Kurdish town of Kobani is an early test of the U.S.-led coalition's patience for a military strategy that at the moment cannot hold ground in Syria.
As President Barack Obama met with top brass at the Pentagon on Wednesday, his administration sought to set low expectations for what U.S.-led air strikes could accomplish in Syria's ground war, and acknowledged Kobani may fall into the clutch of Islamic State, also known as ISIL, in the days ahead.
Secretary of State John Kerry said the loss of the town would not be a strategic defeat. Other officials stressed the focus of the campaign remained Iraq and that air strikes in Syria were intended to initially degrade Islamic State in neighboring Iraq before ultimately destroying them over the long term in both countries.
That strategy, however, requires Western patience that grows thinner with each headline of gruesome Islamic State atrocities and jihadist military victories, or videos depicting beheadings of American or British hostages.
"Evidence is mounting that an 'Iraq first' approach focused on air strikes isn't degrading ISIL. From Kobani to Baghdad they are using their Syrian sanctuary to make gains," said Buck McKeon, chairman of the House Armed Services Committee.
If Kobani fell, Islamic State fighters would control more than half of Syria's 510-mile (820-km) border with Turkey, a NATO ally, which could also face further civil unrest over Ankara's inaction, said Soner Cagaptay at Turkish Research Program at the Washington Institute for Near East Policy.
An Islamic State victory in Kobani could also lead to greater brutality against Kurds on the ground, Cagaptay said. "If Kobani fell, the pictures that would come out of there would be so horrific ... the world's reaction would obviously be sharpened."
The Pentagon cautioned that there are limits to what air strikes can do in Syria before Western-backed, moderate Syrian opposition forces are strong enough to repel them. Obama has ruled out sending American forces on a combat mission there.
"In Syria, right now we just don't have a ground force that we can work with," said Rear Admiral John Kirby, a Pentagon spokesman.
Getting a U.S.-trained ground force in Syria will take time. Kirby cautioned the military will need up to five months to get through the process of recruiting and screening opposition members for a U.S. training program in Saudi Arabia.
"That's before you even start doing any of the training. So this is going to be a long-term effort," Kirby said.
Military experts say the world community must accept occasional setbacks in Syria, at least until those Western-backed forces can move in on the ground.
"We're limited to what's doable from the air (in Syria) and have to be accepting that we're going to have setbacks like this until we can get a proper air-ground operation going," said retired Lieutenant General James Dubik, who oversaw training of Iraqi forces during the Bush administration.
Christopher Harmer, a former Navy aviator who is an analyst at the Institute for the Study of War think tank, cautioned that until then, the Islamic State would rely on tactics to evade being easily targeted from the air.
"Air power is very good at striking static targets - take a bridge, a refinery," Harmer said.
"The problem the strategy so far has had is that you have a bunch of aircraft flying missions against a bunch of dispersed individuals, small infantry forces, and it's clearly not been very effective."
So far, the Pentagon says that fits its strategy, which is designed to stop the Islamic State from using Syria as a "headquarters," a kind of sanctuary to resupply, finance and command troops operating in Iraq.
Even in Iraq, however, progress has been uneven.
That's despite a presence of U.S. military forces advising Iraqi and Kurdish troops and the expansion of U.S.-led air strikes this week to the use of Apache helicopters - which expose American troops to greater risk of ground fire.
"We know that ISIL is going to continue to grab ground and there are going to continue to be villages and towns and cities that they take," Kirby said.
"So when we get up here and we say it's going to be a long struggle and it's going to be difficult, and when we get up here and say airpower - military power alone ... isn't going to be enough to fix it, we really mean it."