President Recep Tayyip Erdogan has said it is not possible for NATO-member Turkey to support Sweden and Finland joining the transatlantic military alliance in the wake of Russia’s invasion of Ukraine, signalling a possible blockade to their anticipated ascension bids.

Speaking to reporters in Istanbul on Friday, Erdogan said Ankara did not have “positive views” on the Scandinavian countries’ expected moves to seek membership, accusing them of being “guesthouses for terrorist organisations”.

“They are even members of the parliament in some countries. It is not possible for us to be in favour,” he said, without providing any further details.

Turkey has repeatedly criticised Sweden and other Western European countries for its handling of organisations deemed to be “terrorists” by Ankara, including the Kurdistan Workers’ Party (PKK) and Syrian Kurdish People’s Protection Units (YPG), as well as the followers of the United States-based Muslim scholar Fethullah Gulen.

Ankara has said Gulenists carried out a coup attempt in 2016. Gulen and his supporters deny the accusation.

Finnish leaders urge NATO bid ‘without delay’

Turkey’s opposition could pose a problem for Sweden and Finland given all 30 NATO allies must unanimously approve a new country becoming part of the United-States led alliance.

Erdogan said it had been an error for NATO to admit Greece, with which Ankara is at odds over a host of issues, in 1952 and urged against “similar mistakes” being made now. Turkey also joined NATO in 1952.

His remarks came after Finland’s president and prime minister on Thursday said the country must apply to join the alliance “without delay” – comments which drew the ire of Moscow and saw the Kremlin threaten to retaliate, including with unspecified “military-technical” measures.

Finland, which shares a 1,300-kilometre-long (810-mile-long) border with Russia, is expected to formally announce its decision on Sunday following a meeting of the country’s senior political figures. Sweden is expected to follow suit.

Responding later on Friday to Erdogan’s remarks, Finland’s Foreign Minister Pekka Haavisto urged patience and called for a step-by-step approach in response to the Turkish resistance. There was no immediate response from Sweden, Al Jazeera reports.