Smoke rises after a shell lands in Kobani in Syria as fighting intensifies between Syrian Kurds and the militants of Islamic State group, as seen from the outskirts of Suruc, at the Turkey-Syria border, Monday, Oct. 6, 2014. Kobani, also known as Ayn Arab and its surrounding areas have been under attack since mid-September, with militants capturing dozens of nearby Kurdish villages. (AP Photo/Lefteris Pitarakis)

WASHINGTON -- For three weeks, Syrian Kurdish fighters, outgunned and outnumbered, have held off an unrelenting assault from the Islamic State on the key city of Kobani. Though Kobani is just across the border from NATO member and anti-ISIS coalition partner Turkey, the Turkish military has merely watched as Turkish leaders tell the world's media that the town is "about to fall."

Meanwhile, the U.S. and its coalition partners have launched just a handful of airstrikes against Islamic State forces in the region -- including a new round of strikes Tuesday morning.

Despite the strikes against additional ISIS forces moving toward Kobani, Syrian Kurds continue to warn that the city could fall to ISIS at any moment: The militants had already moved into parts of the town on Monday, and the fighting is now in the actual streets of the city.

The Kurds warn that if Kobani falls, thousands of its residents will be in danger -- and Turkey will have the Islamic State on its doorstep. What is less understood is that the town's fate could be critical to the administration's stated strategy of supporting non-extremist Syrian rebels in the fight against the Islamic State.

That's because the Kobani battle represents a watershed moment in relations between the U.S.-backed Free Syrian Army and the Kurds: Hundreds of fighters connected to the FSA have put aside their longstanding differences with the Kurds to defend the city against the Islamic State assault. Observers warn that if the U.S. and its partners against the Islamic State cannot get past their own politics to rally behind the Syrian Kurds and the FSA in Kobani, it could undermine faith in the U.S-led coalition's role in Syria.

Though Turkish skepticism toward Syria's Kurds has been pinpointed as a reason the U.S. has not fully embraced Turkey as a partner, parts of the administration see that country as an ally the coalition cannot do without.

In a mid-September hearing on Capitol Hill, Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, said, "If you're asking me how does the opposition in Syria finally prevail against [ISIS], I think it's going to require the assistance of, in particular, Jordanians and probably some of the Syrian Kurds and probably the Turks." And Foreign Policy magazine reported Tuesday that the U.S. has been in talks with the main Syrian Kurdish group, the PYD, and with other Syrian Kurdish groups since 2012.

Right now, those Syrian Kurds do not feel they and their FSA allies in Kobani are getting the support they need from the U.S.-led coalition.

Mohammed Alaa Ghanem, the government relations director for the Syrian American Council in Washington, told The Huffington Post he has been in direct contact with the commander of a 1,500-strong FSA brigade fighting alongside the Kurds in Kobani. Ghanem said he and other interlocutors for the group have been communicating the group's requests for weapons and other support to "the highest levels of the U.S. government" for three weeks as ISIS advanced toward the Kurdish town.

The group, the Ar-Raqqah Revolutionary Brigade, has yet to receive any U.S. assistance, Ghanem said. Ghanem said the group's commander told him he had had to send away at least one-third of his fighters because of limited food supplies in the city.

A State Department official told The Huffington Post on Wednesday evening that he could not provide any specific details on U.S. assistance to the Ar-Raqqah Revolutionary Brigade in Kobani or other Free Syrian Army groups there.

“We’ve been clear that we’ve been providing assistance and that we’re just not able to detail all the types,” he added. “You’re obviously familiar with the airstrikes we’ve been taking in Kobani, six today south of Kobani and nearby. So we’re doing that in an effort to try and help the forces there repel [ISIS].”

The Defense Department did not immediately respond to requests for comment on Ghanem's claims. In her briefing Tuesday, State Department spokeswoman Jen Psaki mentioned coalitions formed in the area by individual opposition groups and said the U.S. is continuing to train and equip the Syrian opposition. She did not mention any groups by name.

Multiple other sources have confirmed some FSA presence in Kobani. A leader of the FSA's Dawn of Freedom Brigades coalition confirmed to the website Syria Comment last week that 250 fighters from his group were aiding Kurds in what they call the Kobani region. And on Friday, CNN said it had been in touch with an FSA fighter in Kobani who said about 300 fighters from the U.S.-backed FSA were in the city.

Center for American Progress national security analysts Michael Werz and Max Hoffman, told HuffPost in a joint email that they believe "the FSA and the [Syrian Kurds] must cooperate or risk annihilation," and that they had heard about FSA support from sources on the ground.

Charles Lister, a visiting fellow at the Brookings Doha Center who studies insurgent forces in Syria, put the number at between 500 and 600 FSA fighters. Lister and others warned that the Kobani battle is being seen as a barometer for U.S. support.

"Rebel groups of all stripes, including hardline Syrian Salafists, have been extremely concerned at the situation in Kobani. This is partly because it represents, for Syrians, the most suitable example of the failure of U.S.-led strikes to roll back or even contain ISIS, but it's also because there is some history of cooperation with the [Syrian Kurdish YPG]," Lister said in an email.

"Morale and perceptions in Syria have become as crucial a battleground as the territory itself in recent weeks," Lister said. "Nearly universally, there is now a patent desire -- within groups of all stripes -- to become more independent from foreign power, simply because on the ground, people perceive this international intervention as entirely self-interested."

Moderate rebels and Syrian civil society actors have already blasted the U.S.-led airstrike campaign for failing to coordinate with them since the strikes in Syria began.

The FSA presence in Kobani is significant because relations between the FSA and the Kurdish PYD have previously been strained. As recently as last year, the parent group of one of the FSA brigades in Kobani was fighting alongside the Islamic State against Kurdish fighters in Aleppo province. Coordination between the two groups would appear to be good news for the U.S. -- but it increases the stakes of the battle, now a testing ground for trust among Syrian partner groups.

The Kurdish militias "say they represent a third way between the regime [of Syrian President Bashar al-Assad] and the rebels, but in practice they've had considerably worse relations with the latter," said Aron Lund, the editor of the Syria in Crisis blog at the Carnegie Endowment for International Peace.

But Aymmen Jawad Al-Tamimi, a researcher on Islamist militants, said in a blog post that there is a "broader trend of some FSA-banner figures coming to terms with past mistakes vis-a-vis" their relationship with Syrian Kurds. Al-Tamimi told HuffPost that FSA cooperation with the Syrian Kurds in Kobani is "the exception rather than the norm" at present.

Still, Al-Tamimi said he does not believe the Syrian Kurds are interested in joining a large-scale push against both the Islamic State and Assad, the main foes of the U.S.-led coalition and the non-extremist Syrian rebels respectively.

Other analysts disagree, describing an FSA-Syrian Kurdish alliance as essential to U.S. goals in the country and the battle against the Islamic State.

"There have certainly been concerns and suspicions on both sides for much of the war, but given the gravity of the ISIS threat and the relative weakness of the moderate Syrian opposition, those are starting to carry less weight," said Werz and Hoffman of the Center for American Progress.

The analysts added that because of this baggage and the geographical separation between areas controlled by the FSA and the Kurdish PYD, the U.S. will have to encourage coordination between the two groups through intelligence-sharing and joint organization.

Any U.S. partnership with the Syrian Kurds would have to overcome two factors: the FSA's concerns about the Kurds' motives and NATO member Turkey's distaste for the PYD.. Though the group has said it does not intend to create a separate Kurdish state, its moves to assert autonomy have worried Turkey and the Iraqi Kurds, just as they have the Arab Syrian opposition.

Asked about the Kurdish reaction to the U.S.-led airstrikes on Tuesday, the Center for American Progress experts -- who published an extensive report on U.S. and Turkish policy toward the Kurds this summer -- said their sources with the PYD "are grateful for the airstrikes but want to see more. They are enraged by Turkey’s role, as Ankara is seen as holding back what would otherwise be a more vigorous response from the US and blocking regional Kurdish aid from reaching the city." Kurds who share that view have staged massive protests within Turkey.

However, reports over the weekend did suggest a new level of engagement between the Turks and the Syrian Kurds. Hurriyet Daily News, a Turkish outlet, said on Sunday that the Turkish government used talks with the leader of the PYD to push him to align openly with the Free Syrian Army and disavow any previous links with Kurdish militants in Turkey. In return, the PYD leader had asked for Turkey to allow arms and sympathetic Kurds to cross its border into Syria.

For the broader U.S.-backed Syrian opposition outside Kobani to reconcile with the Kurds in a similar way, Ghanem of the Syrian American Council said, the PYD would have to prove it had severed ties with Assad. This larger cooperation may hinge on whether the U.S.-led coalition can prove its commitment to the current pocket of FSA-PYD coordination in Kobani.

"It's never too late, so if these strikes actually continue with the same intensity and we're able to dislodge ISIS and push them back, that might restore some of the trust," Ghanem said. That must be "coupled with effective serious cooperation. The U.S. cannot defeat ISIS with aerial power only. The ground forces are guys like these who are willing to sacrifice their lives in the fight against ISIS."