Turkish President Recep Tayyip Erdogan has indicated that Ankara might agree to Finland joining Nato but not Sweden.
He chastised Sweden for refusing to extradite dozens of people suspected of being linked to Kurdish militant groups, as well as other critics of his government.
“If you want to join Nato, you must return these terrorists to us,” Mr Erdogan stated.
His remarks come just days after Turkey halted talks to admit the two Nordic countries as members.
A series of contentious protests in Stockholm, including the burning of a copy of the Koran, prompted the move.
Officials in Sweden condemned the protests while defending the country’s free speech laws.
Sweden and Finland applied to join Nato last year in response to Russia’s invasion of Ukraine, ending decades of military non-alignment.
Their application must be approved unanimously by all current Nato members, but Turkey and Hungary have not ratified their bids.
In his speech, Mr Erdogan suggested Turkey might now “give a different response concerning Finland,” adding that “Sweden will be shocked”.
“We gave Sweden a list of 120 people and told them to extradite the terrorists who were in their country,” Mr Erdogan said. “I apologize if you do not extradite them.”
Sweden has a larger Kurdish diaspora than Finland, and its Nato talks with Ankara have been tense.
Turkey has urged Sweden to distance itself from the Kurdistan Workers’ Party (PKK), which Turkey, the United States, and the European Union consider to be a terrorist organization.
Sweden responded by passing a constitutional amendment that allows it to enact tougher anti-terror laws, as demanded by Turkey.
Sweden and Finland have also lifted bans on selling military equipment to Turkey, which were imposed following Ankara’s military intervention in Syria in 2019.