NATO risks going to war with itself over Syria as tensions between Turkey and other NATO members rise, according to an article published in Newsweek.

At the heart of the crisis are Syrian Kurdish groups, such as the People’s Protection Units (YPG) and Syrian Democratic Forces (SDF), that have received Western backing in the struggle against ISIS. Turkey considers these groups terrorist organizations due to their links to the Kurdistan Workers’ Party (PKK), which has waged an insurgency against the Turkish state for decades. In January this year Turkey and its Free Syrian Army (FSA) allies launched an invasion of Afrin, an area in north-western Syria under YPG control.

The U.S and other NATO members opposed Turkey’s invasion of Afrin, partly because it diverted YPG forces from mopping up operations against ISIS further east.

Now, with Afrin under Turkish control, Ankara continues threatening to expand its military activities in Syria to other areas under the control of Kurdish groups. But U.S. troops are in these areas, raising the risk of armed clashes with Turkey.

To complicate matters, France appears to be stepping up its support for the Kurdish groups in question, with some reports placing French troops on the ground in Syria.

President Emmanuel Macron received an SDF delegation Thursday. He promised his support and according to a statement, "paid tribute to the sacrifices and the determining role of the SDF in the fight against Daesh (the Arabic-language acronym for ISIS), and reaffirmed the priority of this fight while the terrorist threat continues."

Macron also offered to mediate in any dialogue between Turkey and the Kurds.

Ankara was not impressed. "We do not need a mediator. We are extremely saddened by France's entirely wrong stance on this." President Recep Tayyip Erdoğan said on Friday.

Other senior figures in his government were less diplomatic. Deputy Prime Minister Bekir Bozdağ, warned in a series of tweets that, “those who enter into cooperation and solidarity against Turkey,” would, “become the target of Turkey, just like the terrorists.”

A lack of U.S. clarity regarding its intentions in Syria is a further complication. President Donald Trump on Thursday announced that United States would be, "coming out of Syria like very soon." This contradicted previous administration statements that had suggested an open ended military presence in Syria, whilst the Pentagon had likewise declined to give any timetable for a U.S. withdrawal from Syria.