*contributed reporting

Mursitpinar, TURKEY — From the sky, U.S. warplanes have been dropping bombs to impede the advance of militant Islamist fighters on the Syrian border city of Kobani.

On the ground nearby, a formidable array of Turkish tanks and troops appears to be the best-positioned force to turn back the militants with Islamic State, but the Turks’ focus is elsewhere. The military is busy corralling Kurdish activists enraged at the extremist threat to Kobani, a largely Kurdish enclave.

Though the Turkish soldiers can see the militants and hear the American warplanes — and on Monday could glimpse at least one Islamic State flag flying over the eastern outskirts of Kobani as the fighting continued — no one here expects to see their tanks crossing the border any time soon to aid the city’s outgunned Kurdish militiamen.

Nor are the Turks allowing volunteers and military supplies passage to the city, where U.S. air power alone, especially limited by the possible presence of civilians, is unlikely to dislodge the militants as they fight their way into Kobani’s streets.

“If [the Turks] wanted to do something they would have” already, said Huseyn Yuka, mayor of a nearby ethnic Kurdish village, repeating a common refrain among frustrated Kurds. “The border is full of ISIS,” he added, using a common acronym for Islamic State.

The lack of a unified approach between North Atlantic Treaty Organization allies Washington and Ankara is on full display here in the drab, isolated borderlands between northern Syria and southern Turkey.

Since mid-August, when U.S. warplanes began a bombing campaign in neighboring Iraq, President Obama’s stated goal has been to crush Islamic State, which has overrun large swaths of that country as well as Syria. The aerial assault was extended last month to Syria.

The Turks insist they are on board. Last week, their parliament gave the green light for military action in Syria and Iraq, drawing praise from Washington. But Ankara’s role in the campaign against Islamic State remains unclear, beyond providing humanitarian and logistical assistance.

The attack on Kobani, also know as Ayn al-Arab, which began last month, has placed an uncomfortable spotlight on Turkey’s ambivalent role in the U.S.-led coalition confronting Islamic State. Turkish officials have been fending off charges, from Vice President Joe Biden and others, of having helped nurture the terrorist threat in Syria.

The Turks have yet to give permission for U.S. warplanes carrying out airstrikes in Syria to take off from their territory. They say no imminent military action is expected against militants in Syria, though Turkey boasts one of the region’s largest armies and a modern air force equipped with U.S.-built fighters.

The government in Ankara clearly has other priorities, among them toppling Syrian President Bashar Assad’s government and weakening the Turks’ longtime nemesis, the Kurdistan Workers Party, or PKK, which has waged a three-decade war against the Turkish state. For the Turks, bolstering the Kurdish fighters in northern Syria would be akin to aiding the PKK.

“Turkey’s Syria policy is awash with confusing and often conflicting priorities,” Soner Cagaptay, a Turkey analyst with the Washington Institute for Near East Policy, wrote last week. “Turkish policy is to degrade ISIS and Assad alike while also subjugating the PKK.”

It remains to be seen whether Turkey’s objectives can be accomplished, given the complexity of the battlefield and the many layers of proxy conflict, geopolitical rivalries and humanitarian challenges in Syria.

While vowing to fight Islamic State, Turkey finds itself facing both domestic and international constraints. Turkish policymakers fear that a more robust action in Syria could trigger a domestic backlash, even reprisal attacks by Islamic State cells in Turkey. Many people among the country’s Sunni Muslim population sympathize with the Sunni-led rebellion against Assad, a member of the minority Alawite sect, which is an offshoot of Shiite Islam.

“A significant part of the Turkish public believes that the Sunnis of Syria and the Middle East are fellow victims of injustice and that, even if the IS [Islamic State] tactics are repugnant, IS represents a legitimate Sunni grievance,” Hugh Pope, Turkey expert at the International Crisis Group research organization, wrote last week. “This makes it hard for a Turkish government to directly attack IS.”

For years, Turkish diplomats boasted of Ankara’s policy of “zero problems with neighbors.” With the onset in 2011 of the Syrian rebellion, that approach has been sidelined.

Ankara has turned a blind eye to thousands of Syria-bound militants from across the globe who have traversed Turkish territory, nurturing the metastasizing terrorist threat. Turkey’s responses to the charge of allowing its lands to become a superhighway for terrorists have ranged from defensive to incoherent to hysterical.

“Some people are trying to put us into a guilt psychology,” Prime Minister Ahmet Davutoglu, architect of the Syria policy in his former post as foreign minister, told Turkish reporters last month.

On Saturday, Biden issued an apology for comments delivered last week at a Harvard forum in which he said that Turkish President Recep Tayyip Erdogan, whom he described as his “old friend,” had privately acknowledged missteps that fueled the extremist buildup.

“I never uttered such remarks,” an agitated Erdogan told reporters, insisting that “foreign fighters never crossed from Turkey to Syria.”

Feeling pressure from the West, Ankara has recently cracked down on the flow of militants. But diplomatic, intelligence and journalistic accounts have documented the movement of militant Europeans, North Africans, Chechens and others through Turkey to Syria. Turkey has long been a rear base for Syria insurgents of many factions.

“Half of ISIS entered Syria through the Turkish border,” said Sebahat Tuncel, an opposition Kurdish lawmaker who scoffed at officials’ insistence that Turkey has aided only “moderate” rebels fighting Assad. “For two years, Turkey has been sneaking in arms and food and support to the Nusra and ISIS while publicly saying it does nothing,” she added, referring to Al Nusra Front, the official Al Qaeda franchise in Syria.

Turkish officials have said they favor alternative remedies to the Syrian crisis, such as the establishment of a buffer zone in Syrian territory, complete with a “no-fly” mandate. The idea would be to create a refuge for both civilians and Turkish-backed Syrian rebels, who would be shielded from Assad’s warplanes — and, in theory, would be able to defeat both Islamic State forces and the Syrian military. The ambitious plan, which critics call unrealistic, would probably require U.S. air power and a foreign military force on the ground in Syria. Washington has expressed little interest.

Along the Turkish-Syrian border in recent days, there have been periodic clashes between Kurds and Turkish riot police, who used tear gas to disperse crowds angry at the perceived Turkish inaction. Across the border in Kobani, meanwhile, the daily thud of mortar fire and artillery has accompanied the militants’ advance into the city.

“The Turks were able to take Cyprus in about 30 minutes and they had to cross the sea,” said Hassan Hamad, a Kurd who fled Kobani, referring to the 1974 Turkish invasion of Cyprus. “Here they are two meters away and they do nothing.”