“We are currently following the developments regarding Sweden and Finland, but we do not have a positive opinion,” Erdogan told reporters in Istanbul.
Finland and Sweden are expected to submit their membership applications to NATO soon, Xinhua news agency reported.
The Turkish leader, meanwhile, accused the Scandinavian countries of housing terror organisations, such as the outlawed Kurdistan Workers’ Party (PKK).
The PKK, listed as a terrorist organisation by Turkey, has been rebelling against the Turkish government for more than three decades.
As a NATO member, Turkey can veto a country’s admission to the military alliance.