"We find ourselves at a bit of a crisis point in the relationship", Tillerson said.
The limits of US influence in Syria were on display last week during the visit of US Secretary of State Rex Tillerson to Turkey.
The director of the hospital in Afrin, Joan Mohammed, stated that the residents were exposed to poisonous gases used by the Turkish Army in the town of Aranda.
"We agreed our objectives are precisely the same", he said, citing the destruction of Islamic State remnants and stabilizing Syria to allow the return of refugees and people uprooted within the country.
While Tillerson was meeting his Turkish counterpart, Mevlut Cavusoglu, a crowd outside the venue chanted, "Murdering Americans", in a stark illustration of how low bilateral relations have sunk.
"We will work together. we have good mechanisms on how we can achieve this, there is a lot of work to be done", he added.
Kurdish officials said they had informed the United States army about their contacts with Damascus, adding that "the Americans did not mind".
The Turkish military has been advancing slowly in its offensive against Kurdish militias in Afrin.
Despite his determined words, however, Tillerson and Cavusoglu spent much of the news conference repeating positions both have held for months.
Turkey's operation against the YPG, which Ankara blacklists as a terror group, has seen Turkish troops fighting a militia which is closely allied with the United States in the battle against Daesh group militants.
The latest development coincided Friday with a Syrian regime decision to allow Kurds demonstrate in Damascus against the Turkish military operation in northern Syria, carrying portraits of Abdullah Ocalan, imprisoned leader of the PKK. Cavusoglu, the Turkish foreign minister, said Turkey would be able to take joint steps with the United States in Syria once the YPG left the vicinity of Manbij.
Turkey considers the YPG an extension of the banned Kurdistan Workers' Party (PKK), which has fought for Kurdish autonomy in south-eastern Turkey for three decades.
Syrian President Bashar al-Assad's government has had a complex relationship with the YPG during the conflict.
"It's just a fabricated story".
A senior Turkish official has denied the claims by a monitoring group and Syrian state media that Turkey's military used chemical weapons on civilians in its operation against the KurdishYPG fighters in northwestern Syria.
As the talks got underway, dozens of Turkish demonstrators marched to the building where the meeting took place, waving Turkish flags, to protest USA support to the YPG. The sentences against Ahmet Altan, Mehmet Altan and Nazli Ilicak "confirm that the most absolute despotism now reigns in Turkey", Deloire said.
The US support for SDF has infuriated Turkey and created the ongoing diplomatic crisis between the two North Atlantic Treaty Organisation allies.
Canikli also said that Mattis had told him the United States was working on a plan to retrieve weapons given to the YPG, especially heavy weapons.
The Britain-based Syrian Observatory for Human Rights (SOHR) on Friday reported that six civilians had breathing difficulties and other symptoms after a suspected poisonous gas attack.