(Reuters) -- Turkey has lost momentum in the war for northern Syria as the United States draws on Kurdish allies in the assault on ISIS-held Raqqa, but Ankara is still pressing Washington for a deal that allays its fears of Kurdish ascendancy.
Syrian Kurdish groups meanwhile sense Washington is now more firmly behind them than before, a shift they hope will eventually aid their ambitions for autonomy after years of persecution by the Syrian government.
One of the most complicated theatres in the multi-sided Syrian conflict, the war in the north has played out at lightning pace in the last few weeks with ISIS fighters either withdrawing or collapsing in swathes of territory.
The Russian-backed Syrian army has benefited from this, creating a corridor to the Euphrates River that secures Aleppo's water supplies and suggests at least tacit coordination with US-allied Kurdish militia -- at Turkey's expense.
In a swipe at Washington, Turkish Prime Minister Binali Yildirim said on Tuesday it was unfortunate that some of Turkey's allies had chosen the Kurdish People's Protection Units (YPG) as a partner in the fight against ISIS in Syria.
"The field in Syria at the moment is really very complicated," said a senior Turkish official, stressing the fast-moving nature of events and the urgent need for agreement. "Anything could happen at any moment."
"Such a harsh step in completely excluding Turkey there will cause a problem for relations between the countries," the Turkish official said. "Hence a share point must be found. Talks are still continuing."
Turkey has seized a swathe of Syrian land on its southern borders since launching its "Euphrates Shield" operation in August. Its main aim was to prevent creation of a contiguous Kurdish-held corridor it fears could threaten its security.
The rise of Kurdish power in northern Syria has caused alarm in Ankara, which views the Kurdish groups there as an extension of the Kurdistan Workers' Party (PKK) that has been fighting an insurgency on Turkish soil for over 30 years.
Turkey's military chief this week discussed Syria with his US and Russian counterparts. Turkish officials said the first day of talks had focused on ways to guarantee no inadvertent "friendly fire" clashes.
Ankara had hoped to advance its strategy in northern Syria by persuading Washington to abandon its Kurdish allies and switch support to Free Syrian Army (FSA) rebel groups for the final assault on Raqqa -- a northern Syrian city that is ISIS's de facto capital.
But any hopes of this have faded in recent days.
Conflicting US and Turkish agendas have surfaced clearly over Manbij, a city controlled by Kurdish-allied fighters since its capture from ISIS last year. A deployment of US forces there last week deterred a threatened Turkish attack.
Foreign minister Mevlut Cavusoglu made clear Turkish sensitivities about the presence of Kurdish fighters in Manbij, a town Ankara sees as the next stepping stone in creation of a safe zone free of Kurdish influence west of the Euphrates.
"We will not allow the YPG's canton dreams (to come true)," NTV television cited Cavusoglu as saying. "If we go to Manbij and the PYD is there, we will hit them."
The YPG says it withdrew from Manbij after helping to capture it last year, leaving it in the control of allied Syrian Democratic Forces (SDF) -- an alliance that includes the YPG and Arab fighters. Washington has built its strategy around the SDF.