ISTANBUL, Turkey: The head of the North Atlantic Treaty Organization (NATO) on Sunday called on Turkey to drop its opposition to Sweden’s bid to join the United States-led defense alliance, hoping that Stockholm’s accession would be finalized “as soon as possible.”

The call comes as pressure is building on Turkish President Recep Tayyip Erdogan to allow Sweden to become a NATO member ahead of a summit in Lithuania’s capital Vilnius next month.

“Membership will [not only] make Sweden safer, but also make NATO and Turkey stronger,” NATO Secretary-General Jens Stoltenberg told journalists after meeting with Erdogan and his new Foreign Minister Hakan Fidan, who was head of the intelligence agency, in the city of Istanbul.

“I look forward to finalizing Sweden’s accession as soon as possible,” he added.

On Saturday, Stoltenberg attended the inauguration of Erdogan, who was reelected to serve another five years, in a lavish ceremony joined by dozens of world leaders in the capital Ankara.

NATO member Turkey has dragged its feet over admitting Sweden to the alliance. It and Hungary are the only two NATO countries yet to ratify the Nordic nation’s membership bid.

Sweden and Finland dropped decades of military nonalignment and applied to join the alliance in response to Russia’s invasion of Ukraine. Finland formally joined NATO in April.

Erdogan has accused Sweden of being a haven for “terrorists,” specifically for members of the Kurdistan Workers’ Party (PKK), a group blacklisted by Turkey and its Western allies.

“Sweden has taken significant concrete steps to meet Turkey’s concerns,” Stoltenberg said. “This includes amending the Swedish constitution, ending arms embargo, stepping up counter-terrorism operations including against the PKK.”

“Sweden has fulfilled its obligations,” he added.

Swedish Foreign Minister Tobias Billstrom also said Stockholm had fulfilled “all the commitments” to join NATO and urged Turkey and Hungary to admit his country into the alliance.

Ankara is especially displeased with anti-Turkey and anti-Erdogan protests in Stockholm.

Swedish authorities allowed a “No to NATO, No Erdogan Laws in Sweden” demonstration to go ahead in the city center on Sunday.

“Freedom of assembly and expression are core values in democratic societies. But we should remember why these are taking place,” Stoltenberg said.

“Organizers of these demonstrations want to block Sweden’s accession to NATO and undermine its collaboration with Turkey against terrorism and weaken NATO,” he added. “We should not allow them to succeed.”

Stoltenberg said a joint working group established between Turkey, Sweden and Finland at the alliance’s summit in Spain’s capital Madrid last year would meet in the week of June 12, without providing a location.

He also thanked Turkey for deploying additional forces to the NATO-led peacekeeping force in Kosovo.

More than 80 people, including 30 peacekeepers, were injured in a northern Kosovo town on Monday when NATO-led KFOR troops clashed with ethnic Serb protesters who threw rocks, bottles and Molotov cocktails.

In Istanbul, Stoltenberg condemned “unprovoked attacks” against KFOR troops and said: “KFOR and NATO will take all necessary actions to maintain safe and secure environment for all citizens in Kosovo.”