Turkey has been closely following developments regarding the possible NATO membership of Finland and Sweden but does not have a favorable opinion about it, President Recep Tayyip Erdoğan said Friday.

Turkey would not positively welcome Finland and Sweden joining the NATO alliance, he said, describing the initiative as a mistake.

"We do not have a positive opinion. Scandinavian countries are like a guest house for terrorist organizations," Erdoğan told reporters after Friday prayers in Istanbul indicating that Turkey could use its status as a member of the Western military alliance to veto moves to admit the two countries.

Erdoğan said Turkey's former rulers "made a mistake" by giving a green light to Greece's NATO membership in 1952.

"We, as Turkey, do not want to make a second mistake on this issue," he said.

After its powerful eastern neighbor invaded Ukraine on February 24, Finland's political and public opinion swung dramatically in favor of membership as a deterrent against Russian aggression. Finland and Sweden have long cooperated with NATO, and are expected to be able to join the alliance quickly.

Finland's plan to apply for NATO membership, which was announced on Thursday, and with Sweden likely to follow suit, would bring about the expansion of the Western military alliance that Russian President Vladimir Putin aimed to prevent.

While Turkey has usually maintained good relations with Finland, it had some disagreements with Sweden due to the Scandinavian country's support to the PKK's Syrian branch, the YPG, while objecting to Turkey's cross-border operations against the terrorist group in northern Syria.

Turkey has traditionally supported NATO's open-door policy for further expansion. However, Ankara has maintained a neutral position in the Ukraine crisis and assumed a mediator's role by keeping communication channels open with both warring sides.

Since the beginning of the conflict, Ankara has offered to mediate between the two sides and host peace talks, underlining its support for Ukraine’s territorial integrity and sovereignty. While Ankara has opposed international sanctions designed to isolate Moscow, it also closed its straits to prevent some Russian vessels from crossing them.