MADRID: Turkey agreed on Tuesday to abandon its opposition to Sweden and Finland joining the North Atlantic Treaty Organization (NATO), ending an impasse that had clouded a leaders’ summit opening in Madrid amid Europe’s worst security crisis in decades, triggered by the war in Ukraine.

After urgent top-level talks with leaders of the three countries concerned, NATO Secretary General Jens Stoltenberg said “we now have an agreement that paves the way for Finland and Sweden to join NATO,” calling it “a historic decision.”

Among its many consequences, Russian President Vladimir Putin’s invasion of Ukraine has prompted Sweden and Finland to abandon their long-held nonaligned status and apply to join NATO as protection against an increasingly aggressive and unpredictable Russia, which shares a long border with Finland. Under NATO treaties, an attack on any member would be considered an attack against all and trigger a military response from the entire alliance.

NATO operates by consensus, and Turkish President Recep Tayyip Erdogan had threatened to block the Nordic pair, insisting they change their stance on Kurdish rebel groups that his country considers terrorists.

After weeks of diplomacy and hours of talks on Tuesday, Finnish President Sauli Niinistö said the three other leaders had signed a joint agreement to break the logjam.

Turkey said it had “got what it wanted” including “full cooperation…in the fight against” the rebel groups.

Stoltenberg said leaders of the 30-nation group would issue a formal invitation to the two countries to join on Wednesday. The decision has to be ratified by all individual nations, but he said he was “absolutely confident” Finland and Sweden would become members, which could happen within months.

Swedish Prime Minister Magdalena Andersson said the agreement was “good for Finland and Sweden. And it’s good for NATO.”

She also said completing the process of membership should be done “the sooner, the better.”

“But there are 30 parliaments that need to approve this and you never know,” Andersson told the Associated Press (AP).

Turkey hailed Tuesday’s agreement as a triumph, saying the Nordic nations had agreed to crack down on groups that Ankara deems national security threats, including the Kurdistan Workers’ Party, or PKK, and its Syrian extension. They also agreed “not to impose embargo restrictions in the field of defense industry” on Turkey and to take “concrete steps on the extradition of terrorist criminals,” it added.

Ankara has demanded that Finland and Sweden extradite wanted individuals and lift arms restrictions imposed after Turkey’s 2019 military incursion into northeast Syria.

Turkey, in turn, agreed “to support at the 2022 Madrid Summit the invitation of Finland and Sweden to become members of NATO.”

Details of exactly what was agreed were unclear. Amineh Kakabaveh, an independent Swedish lawmaker of Kurdish origin whose support the government depends on for a majority in parliament, said it was “worrisome that Sweden isn’t revealing what promises it has given Erdogan.”

Andersson dismissed suggestions Sweden and Finland had conceded too much.

Asked if the Swedish public would see the agreement as a concession on issues like extraditions of Kurdish militants regarded by Ankara as terrorists, Andersson said “they will see that this is good for the security of Sweden.”

United States President Joe Biden congratulated the three nations on taking a “crucial step.”

Amid speculation about a US role in ending the deadlock, a senior administration official said Washington did not offer any concession to Turkey to coax it to accept a deal. But the official added that the US played a crucial role in helping bring the two parties closer together, and Biden spoke with Erdogan on Tuesday morning at the behest of Sweden and Finland to help encourage the talks.

The agreement came at the opening of a crucial summit, dominated by Russia’s invasion of Ukraine, that will set the course of the alliance for the coming years. Top of the agenda in meetings on Wednesday and Thursday is strengthening defenses against Russia and supporting Ukraine.