A US-backed offensive to seize control of Raqqa, the Syrian stronghold of the Islamic State (also known as ISIS), has become enmeshed in bitter conflicts between Washington’s main allies on the ground.

The opening of the drive south toward the city was first announced last Sunday by President Barack Obama’s counter-ISIS envoy, Brett McGurk, who proclaimed that the “initial phase” of the operation to liberate Raqqa, dubbed “Euphrates Wrath”, had begun.

What has followed, however, has been a series of recriminations between Turkey, Washington’s main NATO ally in the region, and the Syrian Kurdish forces of the Popular Protection Units (YPG) militia, which constitutes the principal proxy force in the drive against Raqqa. The YPG has been armed and funded by the Pentagon and accompanied into battle by US special forces units.

The government of President Recep Tayyip Erdogan initiated its own intervention into Syria, “Euphrates Shield,” beginning last August. Ostensibly launched in support of US-led operations against ISIS, the main thrust of the Turkish offensive has been directed at consolidating its own buffer zone along the Syrian-Turkish border and preventing Kurdish forces from joining together the territory they control in the same area.

With the so-called Syrian Democratic Forces (SDF), dominated by the Kurdish YPG, pushing further south toward Raqqa and seizing control of villages on the way, the Erdogan government has grown increasingly agitated, fearing that a successful offensive will strengthen the Kurdish enclave on Turkey’s border.

Ankara considers the YPG a branch of the PKK (Kurdistan Workers’ Party) in Turkey, regarding both as “terrorist” groups.

Gen. Joseph Dunford, the chairman of the US Joint Chiefs of Staff, was dispatched to Turkey on Monday for talks with his counterpart, General Hulusi Akar, on the offensive against Raqqa.

In his discussions with the Turkish general staff, General Dunford attempted to assuage Ankara’s hostility to the role being played by the Kurdish militia and made promises that the YPG-led SDF would not take Raqqa. According to the Pentagon’s web site, Dunford told Ankara that the Kurdish militia was moving south “to isolate the enemy that’s in the vicinity of Raqqa and in Raqqa,” in an operation that would take months.

“We always knew the SDF wasn’t the solution for holding and governing Raqqa. What we are working on right now is to find the right mix of forces for the operation,” the top US commander said. He claimed that the Pentagon would rely upon “the moderate Syrian opposition, the vetted Syrian forces and the Free Syrian Army forces.” “Moderate,” “vetted” and “Free Syrian Army” forces all refer to the same fiction of a viable secular, US-backed opposition capable of mounting a major military operation. Such forces simply do not exist. US officials have acknowledged that the main forces that have benefited from the vast amounts of money and weapons poured into Syria by Washington and its regional allies have been the Al Qaeda-linked militias such as ISIS and the Al Nusra Front.

In addition to the issue of the Kurdish advance on Raqqa, Turkish officials pressed Dunford on the continued YPG occupation of Manbij, a city in northern Syria west of the Euphrates River. Washington had previously told the Turkish government that the YPG, which seized Manbij from ISIS last June, would withdraw from the town, which Ankara sees as linking up Syrian Kurdish “cantons” in the east and west of northern Syria.

Foreign Minister Mevlüt Çavuşoğlu charged on Tuesday that some 200 YPG fighters are still in Manbij, warning that unless Washington saw to their withdrawal, Turkey would take “necessary actions.”

Speaking before a parliamentary committee, Çavuşoğlu also touched upon Dunford’s promises regarding Raqqa. “The YPG will only serve in seizing, as operations in the city will be conducted by special forces along with local forces. This is the agreement we have reached with the US, but we are still walking on thin ice as to whether they keep their promise or not, as we have experienced with Manbij.”

The Associated Press quoted a Pentagon official as saying that Dunford had not guaranteed that the Syrian Kurdish fighters would not go into Raqqa, only that the US would “work with” Turkey on organizing the final offensive against the city.

For its part, the YPG and SDF leadership have insisted that they will continue their offensive into Raqqa itself and have categorically rejected any Turkish role in the offensive.

Further complicating the situation, the minority of Syrian Arab fighters affiliated with the SDF have pulled out of the offensive, claiming that they have been double-crossed by the Kurdish militia and its American advisors.

According to a statement quoted by the web site Middle East Eye, the Syrian Arab brigade charged that the US was attempting to “sideline” its participation, while relying exclusively on Kurdish forces. It claimed this violated an agreement that the YPG “would only provide logistical support for the operation” and that the Syrian Arab fighters “would be in charge of the administrative and security management of the city afterwards.”

The charges appeared to echo concerns expressed by Ankara that a Kurdish invasion of Raqqa could lead to a form of ethnic cleansing of what has long been an overwhelmingly Arab city.

There is also the possibility that an attempt to seize the city with the Kurdish militia could provoke a response from the government of President Bashar al-Assad, backed by Russia, again raising the threat of a wider war.

Meanwhile, the Erdogan government appears to be hopeful that it can achieve a more favorable agreement with an incoming Donald Trump administration regarding Syria and the Kurds. While Erdogan had earlier condemned candidate Trump’s call for a ban on all Muslims entering the US, he delivered one of the earliest and most effusive messages of congratulation to the new president-elect.

An indication that the desire for rapprochement may be mutual came in the form an article published this week by The Hill, by Trump’s senior national security advisor, retired General Michael Flynn, the former head of the Defense Intelligence Agency.

Flynn criticized the Obama administration for “keeping Erdogan’s government at arm’s length—an unwise policy that threatens our long-standing alliance.”

Flynn went on to strongly suggest that the US should agree to Ankara’s demand for the extradition of exiled Islamic leader Fethullah Gulen, who resides under US government protection in Pennsylvania. The Erdogan government has blamed Gulen for the abortive July 15 military coup against his government and has carried out a massive purge of his suspected followers.

“It is time we take a fresh look at the importance of Turkey and place our priorities in proper perspective,” Flynn writes. “It is unconscionable to militate against Turkey, our NATO ally, as Washington is hoodwinked by this masked source of terror and instability nestled comfortably in our own backyard in Pennsylvania... We should not provide him safe haven. In this crisis, it is imperative that we remember who our real friends are.”