The United States is pushing Turkey to join the fight against Islamic militants, amid frustration and wariness in both governments heightened by Ankara's unease at helping besieged Kurdish communities.
Retired US general John Allen, and the US pointman on Iraq, Brett McGurk, will Thursday begin two days of talks in Ankara seeking to squeeze commitments from Turkey on what role it will play in the US-led coalition battling hardline Islamic militants, who have seized control of a large swath of its southern neighbours Iraq and Syria.
"There is frustration and anger among the Americans, and yet at the same time, they realise that the Turks are in a difficult position," said Bayram Balci, an expert with the Carnegie think-tank in Washington.
"They know that the Turks have 'good reason' not to intervene," he added.
Syria-based Kurds are fighting against the Islamic State (IS) group in the besieged town of Kobane.
The Kurds, fighting with People's Defense Units (YPG), are affiliated with PKK militants who have fought the Turkish authorities for the last three decades in an insurgency that has claimed 40,000 lives.
Since the start of the Syrian civil war over three years ago to oust Syrian President Bashar al-Assad, Turkey has been caught in the cross-hairs. It has taken in some 1.5 million Syrian refugees, and also sought to expel foreign fighters trying to cross into Syria.
But there is US dismay that, despite a parliamentary green light last week, Turkey has not yet committed its well-equipped and well-trained military to the fight.
- Why Turkey? -
Military experts say US airstrikes can help the people of Kobane, but they are not enough to stop the IS march -- that what is needed is boots on the ground.
Indeed Turkish President Recep Tayyip Erdogan this week called for a ground operation to save Kobane, saying: "I am telling the West -- dropping bombs from the air will not provide a solution."
But he stopped short of offering up Turkish troops to aid the town.
US President Barack Obama has ruled out sending in US troops, so for the Turks, the question is "why me?" said Marina Ottaway, a senior scholar with the Wilson Center.
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Ankara has also been angered over the years by Obama's refusal to act more decisively to aid the moderate Syrian opposition in their bitter fight to topple Assad.
"You have, I think, a long-standing Turkish frustration about being expected to take the brunt of the fighting, while the United States until very recently was doing nothing," said Ottaway.
"Obama did nothing for a long time when Turkey was trying to get him to do something, and then, all of a sudden, because Obama finally changed his mind, everybody is expected to jump to the US policy."
In a sign of the difficulties and tensions, US administration officials Wednesday sent mixed messages about the possibility of creating a safe haven along the Syrian-Turkish border -- one of Erdogan's key demands.
"There’s growing angst about Turkey dragging its feet to act to prevent a massacre less than a mile from its border," a senior administration official told the New York Times.
"After all the fulminating about Syria’s humanitarian catastrophe, they’re inventing reasons not to act to avoid another catastrophe."
- Direct threat -
US officials, however, have publicly downplayed any notion that they are dismayed by Ankara's reluctance, saying they are in "active discussions" with the Turks, while refusing to outline exactly what they want their NATO ally to do.
"I think there’s a recognition ISIL poses a direct threat and a neighbouring threat to Turkey... clearly we think they can do more," State Department spokeswoman Jen Psaki said.
"Certainly they have their own concerns to be focused on, and that’s one of the reasons why they need to play a pivotal role here."
An over-riding fear for Turkey is that the standoff around Kobane could lead to the creation of a Kurdish fighting force overlapping the Turkish and Syrian borders.
And a senior State Department official has admitted that it was "a challenge" to get Ankara to move beyond its antipathy towards the Kurds.
But White House spokesman Josh Earnest insisted: "The stake that Turkey has in the outcome here is significant and very direct. It is not in the interest of that nation for this kind of violence and instability to be emerging literally on their doorstep."