The Syrian Kurdish People’s Protection Units (YPG) said on Tuesday, June 5, that its military advisors would leave the city of Manbij, Syria, following a Turkish-American agreement that mandated the withdrawal. The new roadmap provides for Turkish and American joint security in the city after the departure of the YPG advisors. The move, however, is unlikely to smooth over the widening rift in Turkish and American relations.

According to a YPG statement, fighters left Manbij in November 2016, though military advisors stayed behind to advise the Manbij Military Council (MMC). The roadmap will reportedly be implemented within the next six months and will involve moving YPG personnel east of the Euphrates River. Some of the plan’s details remain vague, however, and could cause contention between Turkey, the U.S. and the latter’s Kurdish allies to flare if the plan’s implementation does not meet Turkish expectations.

The MMC is a militia allied with the American-supported Syrian Democratic Forces (SDF) in northern Syria. The group announced on Wednesday, June 6, that the Kurdish YPG militia would withdraw its military advisers in the coming days. However, the group made it clear in a statement that its forces would “heed the call when necessary to offer support and help to the people of Manbij should it be needed.”

Turkey, however, views the withdrawal as more definitive. During a speech on June 5, Turkish Foreign Minister Mevlut Cavusoglu stated that “in the first phase, terrorist YPG will withdraw from Manbij. They will move to the east of the Euphrates. However, that does not mean we will accept that they stay there,” reported Anadolu Agency.

Turkey has long criticized the U.S.’s backing of the SDF, especially the YPG, which it views as a terrorist organization linked to the illegal Kurdish Workers Party (PKK) that operates within Turkey. In January 2018, Ankara initiated a military attack against the YPG, threatening to force Kurdish troops from Manbij if they did not withdraw. Cavusoglu stated that the YPG troops would be stripped of their weapons during the process of withdrawal and that the roadmap, which had been agreed to by American Secretary of State Mike Pompeo, would be executed within the next six months. The U.S., however, has made no promises to label the YPG a terrorist organization or to adhere to Turkey’s timeline, suggesting the deal is ripe for misunderstandings between Ankara and Washington.

Ankara’s pledge to remove YPG troops raised American concerns that Turkish and U.S. forces in the region might have to confront each other. The U.S. could then find itself in the position of having to choose between fighting a NATO ally or having to turn on its Syrian proxy forces. Controversy over the YPG has led to other problems between the U.S. and Turkey over the last year. On March 17, Turkish forces took control of Afrin, Syria, after a two-month offensive against the YPG. The U.S. and Germany criticized Turkey, but Erdogan dismissed their concerns, claiming falsely that no civilians were wounded in the siege.

Tensions rose between the U.S. and Turkey when Ankara announced in December of last year that it would go ahead with its decision to buy S-400 surface-to-air missiles from Moscow. In response, a U.S. Senate committee voted to approve a $716 billion defense policy bill on May 24, effectively blocking Turkey from purchasing Lockheed Martin F-35 jets. The U.S. also criticized Turkey for imprisoning Andrew Brunson, an American pastor, on terrorism charges. Ankara claims that the YPG roadmap will have no effect on its Russia deal, which is already underway and is not an alternative to Turkey working with Russia in Syria.

While the U.S. appears to have some hesitations with regards to the roadmap’s implementation, Turkey views the recent plan as a positive move and a potential turning point for U.S. and Turkish relations over Syria, the YPG withdrawal agreement being claimed as a victory against the PKK during the June 24 elections.

The YPG has been an important ally for the U.S. forces and is considered one of the most effective groups in the fight against the Islamic State (IS). The primarily Kurdish militia was founded in 2004 and makes up a key component of the Democratic Federation of Northern Syria’s Syrian Democratic Forces. Its numbers grew quickly during the Syrian Civil War, and it became the dominant Kurdish group in the region along with its sister group, the Women’s Protection Units (YPJ).

During the 2015 Siege of Kobanî, the YPG won a major victory against IS with ground and air support from the U.S. Later that year, the YPG, under the SDF banner, led the military campaign for the liberation of Raqqa, the former IS capital. The militia allegedly withdrew from Manbij in November after its victory against IS, however, military advisors remained at the request of the MMC to provide training to local forces.