The fight against Islamic State militants could at last win Syria's Kurds the Western help they have sought, but they must first clarify their relationship to President Bashar al-Assad and reassure Turkey that they won't cause trouble on its border.
The United States has entered the war against Islamic State fighters in Iraq with airstrikes, but is still trying to decide a strategy for fighting the group on the other side of the frontier in Syria.
In Iraq, Kurds are one of the main Western allies against the Islamic State group.
But in Syria, where Kurdish militia have carved out a swath of northern territory and repeatedly battled against Islamic State fighters during a three-and-a-half year civil war, Kurds have yet to win the West's acceptance as partners.
The main Kurdish political party in Syria, the PYD, and its armed wing, the YPG, say they are obvious allies for Western states as the only force with a proven track record of combating Islamic State there.
The Kurds are dismissive of the moderate Syrian opposition that has been backed by the West but outgunned by Islamist groups.
But the West has so far kept Syria's Kurds at arm's length.
NATO member Turkey has concerns over the PYD's historic links to the separatist PKK that fought for Kurdish rights on the Turkish side of the border. And pro-Western Syrian opposition groups accuse the PYD of having cooperated with Assad's government to take control of territory in 2012, which the Kurds deny.
Contact with foreign officials
Since Islamic State militants overran the Iraqi city of Mosul in June, the PYD has been offered a chance to address both issues in a flurry of contacts with foreign officials, including some from “major powers,” said Khaled Eissa, PYD representative in France.
He declined to identify the countries involved, citing diplomatic protocol.
“They have given us signals that their position towards us is changing. But in my analysis - based on the contacts I mentioned - there are still obstacles,” Eissa said by phone.
“They know the YPG are the most effective force against (Islamic State). They want more assurances for the Turkish side,” Eissa said. “NATO states allied to Turkey must reassure it and make it understand that Islamic State's existence is also a danger to Turkey and that the PYD does not wish ill on anyone.”
The foreign contacts increased last month when Islamic State fighters in Iraq besieged thousands of members of the ancient minority Yazidi sect atop a desert mountain, which U.S. President Barack Obama described as a potential genocide.
YPG fighters crossed into Iraq to help evacuate the Yazidis. That role improved the PYD's image, a Western official said.
“I don't anticipate a major change of policy, but I do anticipate greater dialog with the PYD.”
Little contact with West
Redur Xelil, YPG spokesman, said the group had met U.S. military officials on the mountain, Mount Sinjar, to discuss the Yazidi evacuation. But apart from that, there had been no contacts between the armed group and the West, he said.
“We hope for strong cooperation with American or European states in the fight against Islamic State - be it either in Syria or Iraq,” he said, speaking by telephone.
Kurds live in Turkey, Iran, Iraq and Syria, and many have long dreamed of a state of their own. The closest they have come is in Iraq, where they rule an autonomous region that has managed to assuage concern from its neighbors and win support from the West.
Germany, Britain, France and Italy have all said they will arm Iraqi Kurdish security forces fighting Islamic State militants.
The Kurds in Syria have received no such help in crucial battles against Islamic State fighters, whose arsenals have become far more potent since June with weapons seized from the Iraqi and Syrian militaries.
In July, the YPG fought off a major Islamic State attack on Kobani, a Kurdish city also known as Ain al-Arab that is important because of its location on the Turkish border. Kurdish fighters crossed into Syria from Turkey to help in the fight.
On the offense
Ocalan Iso, a Kurdish military commander in Kobani, says YPG fighters are now taking the fight to the Islamic State group in nearby areas used as operational bases by the Islamists.
The YPG has also been battling Islamic State fighters at the Iraqi border. It said 35 of its fighters were killed in a two-week battle for control of the village of Jazaa at the frontier.
The YPG said it has killed hundreds of Islamic State fighters.
Syrian Kurds worry that if Islamic State fighters are driven from Iraq they will become an even bigger threat in Syria. “It won't be enough to bomb their positions in Iraq. If Obama or America bombs their positions in Syria, there must be coordination with the Kurdish forces,” Iso said.
He estimated the size of the YPG at 50,000 fighters.
It is not yet clear what the United States will do about Islamic State fighters' foothold in Syria, where U.S. decision-making is complicated by its opposition to Assad.
Western states that have backed the uprising against Assad have rebuffed the Syrian government's call for cooperation against Islamic State.
Obama has authorized air surveillance over Syria, a decision that prompted speculation he was on the brink of ordering airstrikes on the group there, but these do not appear imminent.
Part of his plan is to enhance support for moderate Sunni Arab groups, who are fighting against both Assad and the Islamic State group. The Kurds say they are cooperating with the same groups, notably in a battle for territory north of Aleppo.
Human rights monitor
The Syrian Observatory for Human Rights, which monitors violence in the Syrian war, has recently recorded cooperation between Sunni Arab rebels and Kurds in the area, the organization's founder Rami Abdulrahman said.
For such cooperation to take hold, the Syrian Kurds and moderate Sunni Arabs must shelve suspicions of each other's aims. Aleppo could be a test case. The Islamic State militants' advance in territory north of the city is threatening supply lines for other Sunni Arab groups and also poses a risk for Kurdish interests in the town of Afrin and elsewhere.
Noah Bonsey, senior analyst on Syria at the International Crisis Group, said there was “potential value added” in military cooperation between the Kurds and moderate Sunni Arabs against the Islamic State group.
“The most obvious test case for this is Aleppo because the stakes are very high for everyone involved,” Bonsey said. “There are plenty of shared interests there, and there are some local relationships that exist. But those relationships would have to develop significantly to enable meaningful coordination.”