“If you cannot show this respect, then sorry but you will not see any support from us on the Nato issue,” Erdoğan said after a Cabinet meeting in Ankara on Monday, without indicating whether or not that meant the door for negotiation was now closed.

“Those who promote and turn a blind eye to this perversion have undoubtedly taken into account its consequences,” he said.

Erdoğan’s comments render Sweden and neighbouring Finland’s efforts to join Nato a more distant prospect, given the approval of Turkey’s Parliament is required for the move to go ahead. At least 28 of 30 Nato members have ratified the Nordic applications, and Hungary has said it plans to do so at the opening of Parliament next month. That would leave Turkey as the lone holdout to the expansion, which Nato diplomats had hoped to finalise in time for the alliance’s summit in Vilnius in July.

Turkey had agreed in principle to Nato allies including the US inviting Sweden and Finland to join the group, but went on to demand concessions from Sweden. Those included a broader crackdown on Kurdish groups that Turkey considers terrorist organisations alongside the extradition of suspects.

Turkey is sensitive about any hostile act towards Islam, and the President is looking to strengthen support from nationalists and the religiously conservative ahead of elections expected in May.

Danish far-right activist Rasmus Paludan set fire to a copy of the Koran near the Turkish embassy in central Stockholm on Saturday. Paludan (41), who also has Swedish citizenship, has made a name for himself through a number of provocative Koran burnings, which last year led to protests and riots in Swedish suburbs where many residents are Muslim.

Paludan, who has been convicted of racism and defamation in Denmark, told a populist right-wing news site before the event that his aim is to promote freedom of expression.

Part of Democracy

“Freedom of expression is a fundamental part of democracy, but what is legal is not necessarily appropriate,” Swedish Prime Minister Ulf Kristersson said on Twitter on Saturday. “Burning books that are holy to many is a deeply disrespectful act. I want to express my sympathy for all Muslims who are offended.”

Turkey cancelled a planned visit by Swedish Defence Minister Pal Jonson after the incident, which followed the hanging of an effigy of Erdoğan in Stockholm by protesters affiliated with Kurdish movements.

Asked on Monday about Erdoğan’s comments, Finnish Foreign Minister Pekka Haavisto called the burning “an unfortunate event” but said that “security in the entire Nato area” should be the priority.

Nato Secretary-General Jens Stoltenberg said he’s in close contact with officials in Sweden, Finland and Turkey.

“Of course I am against the kind of behaviour that we have seen on the streets of Stockholm but this is not something that is illegal and freedom of speech is a very precious right,” he said, speaking through a translator.

Sweden has insisted that it’s in compliance with an agreement hammered out at Nato’s June summit in Madrid last year, which allowed the expansion process to move forward.

“If you love and protect members of the terrorist organisation and enemies of Islam so much, then we advise them to refer the defence of their country to them,” Erdoğan said.

(With assistance from Beril Akman, Leo Laikola, Niclas Rolander, Kati Pohjanpalo and Iain Rogers.)