The four-way talks between Türkiye, NATO, Finland, and Sweden have begun on Tuesday on the sidelines of the NATO summit in Madrid.
Türkiye's President Recep Tayyip Erdogan, NATO Secretary-General Jens Stoltenberg, Finland's President Sauli Niinisto, and Sweden's Prime Minister Magdalena Andersson will discuss the Nordic countries' bids to join the alliance as well as Ankara's concerns on the matter.
Sweden and Finland formally applied to join the alliance last month, a decision spurred by Russia's war on Ukraine.
But Türkiye, a longstanding member of the alliance, has voiced objections to the membership bids, criticizing the countries for tolerating and even supporting terrorist groups.
Stoltenberg has constantly said that Türkiye has "legitimate concerns related to their fight against the PKK terrorists group and other organizations," and that the PKK is considered a terror organization by NATO, the EU, as well as Finland and Sweden.
In its more than 35-year terror campaign against Türkiye, the PKK has been responsible for the deaths of more than 40,000 people, including women, children and infants.