A permanent rupture in the U.S.-Turkey relationship over U.S. support for the PKK terrorist organization's Syrian affiliate, the Democratic Union Party's (PYD) People's Protection Units (YPG), would be a loss for both sides and a big win for Daesh, the U.S.-based NGO Turkish Coalition of America (TCA) warned.

A letter penned by TCA President G. Lincoln McCurdy that was published Monday in the Washington Times said that Turkey justifiably perceives the U.S. armament of the YPG as a national security threat after terror attacks on its border killed dozens of Turkish soldiers.

McCurdy said the Trump administration fails to acknowledge Turkey's decadeslong fight against PKK and provide guarantees that the equipment being provided to the YPG will not end up in the hands of PKK terrorists.

"We urge the U.S. to reconsider its decision on arming the YPG-PKK and recommit to its strategic partnership with Turkey," the letter read.

The U.S. government has long supported the YPG terrorist group with a vast amount of military equipment and heavy armament to fight Daesh. Despite Ankara's concerns, former U.S. President Barack Obama initiated the support program, which so far has sent nearly 5,000 truckloads and 2,000 planeloads of weapons. This has been continued by the Trump administration.

The lack of consistency from the Trump administration regarding the U.S.'s activities in Syria has fueled tensions and deepened the rift in relations with Turkey that were already complicated.

In November 2017, Trump assured Erdoğan that the U.S. will no longer provide weapons to YPG, a promise he reiterated in Wednesday's phone call, according to the sources. However, the Turkish side soon turned skeptical of Trump's promise after Pentagon said it was reviewing "adjustments," suggesting such decisions would be based on battlefield requirements.

The Pentagon's reluctance to comply with Trump's decision became clearer after it allocated $500 million worth of weaponry, ammunition and vehicles in its 2018 budget to the YPG-dominated Syrian Democratic Forces (SDF) to fight against Daesh.

In January, Turkey was alarmed once again after the U.S.-led coalition announced its plans for a 30,000-strong border security force composed of YPG-led SDF fighters that would be deployed along the Turkish border. Following a strong reaction from Turkey, Pentagon said it did not intend to create an "army" or conventional border guards.

U.S. Secretary of State Rex Tillerson later said Washington owed Turkey an explanation over "border force" reports in an attempt to control the damage.