Turkey has accused the US of not supporting its military operations against Daesh. Ankara is now using the key Incirlik military air base, located in the country's southeastern Adana province, as a bargaining chip.
The base has been important for NATO and the US in fighting against Daesh, and also enables aircraft in the US-led coalition to reach their targets without having to refuel mid-air.
The situation "naturally causes Turkey to question the use of Incirlik [air base]," Turkish Defence Minister Fikri Isik said earlier this month.
Turkish Foreign Minister Mevlut Cavusoglu said Turkish nationals are also asking why the US is using the base if they aren't supporting Turkey's Operation Euphrates Shield.
Turkey's relations with the United States and the West have been damaged since rogue commanders linked to US-based cult leader Fethullah Gulen allegedly attempted to overthrow the Turkish government on July 15 last year.
Although Turkey has never shut down the air base completely, it has from time to time suspended flights from Incirlik Air Base, the last time being the day after July's failed coup.
Turkey arrested dozens of commanders, including the head commander of the Incirlik military base, in connection to the attempt.
Turkey can shut it down. But...
Soli Ozel, a journalist and academic in International Relations at Kadir Has University, told TRT World that if Turkey decides to shut down Incirlik Air Base, it can.
"It would be like taking a step which would be difficult to reverse. It also sends a very radical message," said Ozel.
He said Turkey's strategic partnership would be suspended and relations with NATO will begin to be questioned.
"There are already some members that want to learn whether Turkey wants to leave NATO or not. These kind of questions will gain power," Ozel added.
US-Turkish ties were also strained over Turkey's Operation Euphrates Shield, which began in August. The cross-border operation aims to clear northern Syria of groups that Turkey deems hostile, including Daesh and the YPG.
But for the large part Turkey has been alone in its operations. Ankara has criticised the West for its lack of support in the fight against both domestic and external terror threats.
US-led anti-Daesh coalition spokesperson John Dorrian said in Baghdad last week that the US is in diplomatic talks to support Turkish forces in an operation to liberate the Syrian town of al-Bab from Daesh.
Pentagon spokesman Peter Cook said last week that the US carried out flights in support of Turkish troops at the request of Turkey near al-Bab.
The US-led coalition has refrained from supporting Operation Euphrates Shield.
The US has been providing weapons and ammunition to the YPG, an affiliate of the PKK, in the fight against Daesh. While the PKK is considered to be a terror organisation by both Turkey and the US, Ankara says the US does not treat the PKK's Syrian affiliate as such.
The Turkish foreign minister mentioned last week that Turkey and the US are experiencing a "confidence crisis."
How can the YPG issue be solved?
Prof. Cagri Erhan, Istanbul Kemerburgaz University rector and International Relations expert, told TRT World there are three conditions to be met that could solve the disagreement between the US and Turkey over the YPG.
Erhan said "a one-on-one meeting" Turkish officials should arrange a meeting with the Trump administration and the "Turks should stress that Turkey and the US are allies, and support of the YPG is unacceptable."
Secondly, Turkey should put the issue to North Atlantic Council, which is the principal political decision-making body of NATO.
"There is a permanent committee (Permanent Representative Level) that gathers weekly in ambassadors level … Turkey [on that committee] should put the issue on the table with evidence," Erhan said.
Finally, Erhan said that Turkey should inform and convince "pressure groups" about the relationship between the YPG and the US.
"By using social media and public diplomacy, by establishing relations with NGOs, by sending committees to the US Congress, by holding conferences in universities, etc., Turkey should tell clearly that the US indirectly supports a terrorist group," Erhan said.
"This is the way how the American politics work," he said.