Turkish President Tayyip Erdogan’s spokesman on Sunday denounced efforts by the U.S.-led coalition to train a border security force in northern Syria including Kurdish YPG fighters as worrying and unacceptable.

Ibrahim Kalin said that, instead of ending support for the YPG, as Ankara has requested, “the USA is taking worrying steps to legitimise this organisation and make it lasting in the region. It is absolutely not possible for this to be accepted.”

Turkey considers the YPG to be an extension of the outlawed Kurdistan Workers Party (PKK), which has waged an insurgency in southeast Turkey since the 1980s. Ankara “will continue its fight against any terrorist organisation regardless of its name and shape within and outside its borders”, Kalin said.