BRUSSELS (AP) — NATO Secretary-General Jens Stoltenberg conceded Wednesday that Turkey has blocked efforts to let Finland and Sweden join the world’s biggest security alliance at the same time, and said he is heading to Ankara to discuss the issue with the Turkish president and foreign minister.

Finland and neighboring Sweden abandoned decades of nonalignment and applied to join the 30-nation alliance in the wake of Russia’s invasion of Ukraine a year ago. All NATO members except Turkey and Hungary have ratified their accession, but unanimity is required.

Stoltenberg and most allies have long insisted that the Nordic neighbors should join at the same time.

But Turkey has accused the government in Stockholm of being too lenient toward groups it deems as terror organizations or existential threats, including Kurdish groups. Earlier this month, Turkish Foreign Minister Mevlut Cavusoglu said Ankara has fewer problems with Finland joining.

“There are different assessments in Turkey about to what extent Finland and Sweden are in the same position to be ratified, and that is a Turkish decision,” Stoltenberg told reporters, after chairing a meeting of NATO defense ministers.

“That’s not a NATO decision. It’s a decision by Turkey,” he said, while underlining his belief that both countries have fulfilled their commitments to NATO and Turkey and should be allowed to join.

Stoltenberg added that “the sequencing is not the most important thing. The most important thing is that both Finland and Sweden soon become members of the alliance,” breaking with a stance he has voiced for many months that it was important that they join together.

But the former Norwegian prime minister did not criticize Turkey. The country was rocked last week by a devastating earthquake and aftershocks that killed more than 39,000 people there and in neighboring Syria.

Turkey is also in an election year, and the topic of Nordic membership of NATO is a possible vote winner.

In recent weeks, President Recep Tayyip Erdogan has expressed anger at a series of separate demonstrations in Stockholm. In one case a solitary anti-Islam activist burned the Quran outside the Turkish Embassy, while in an unconnected protest an effigy of Erdogan was hanged.

Swedish Prime Minister Ulf Kristersson has said it would be “unfortunate” if Finland entered NATO first.

Stoltenberg was due to fly to Ankara later Wednesday and meet Erdogan and Cavusoglu.

U.S. Defense Secretary Lloyd Austin declined to take a stand, but he said that NATO has trained with both candidate countries and praised them for investing in modern military equipment.

“They are ready to join now, and these are two countries that are highly capable, that bring a lot of value to the alliance once they join,” Austin told reporters.

Of the two countries, only Finland shares a border with Russia and would appear to be more at risk should Russian President Vladimir Putin decide to target his neighbor. That said, some NATO allies, led by the United States, have offered security guarantees to both should they come under threat.

Hungary has pushed back its ratification date for both countries three times so far but has not publicly raised any substantial objections to either of them joining.

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