Secretary General Jens Stoltenberg said on Wednesday that it is still possible to reach an agreement with Türkiye on Sweden's NATO accession before the leaders' summit in July.
"It is still possible to have an agreement before the Vilnius summit," Stoltenberg told reporters at a news conference in Brussels.
His remarks came as representatives from Türkiye, Finland, Sweden, and NATO gathered for a meeting earlier on Wednesday in the Turkish capital Ankara.
Stoltenberg said that according to his information, the meeting of the joint permanent mechanism in Ankara "took place in a constructive atmosphere."
"Some progress had been made, and we will continue to work" such that Sweden's NATO membership is ratified as soon as possible, he added.
He stressed that following Türkiye's request, Sweden "changed the Constitution, strengthened the counter-terrorism laws and lifted restrictions on arms export to Türkiye."
He also welcomed the recent announcement on the extradition of a person affiliated with the PKK terrorist organization to Türkiye.
"This is good for the fight against terrorism, but also good for Sweden's efforts to fight organized crime," he asserted.
"These groups are linked," he said, explaining that the same people conducting organized crime in Sweden are also responsible for terrorist actions in Türkiye.
Although Türkiye approved Finland's membership to NATO, it is waiting for Sweden to abide by a trilateral memorandum signed last June in Madrid to address Ankara's security concerns on terrorism.
A new Swedish anti-terror law allows authorities to prosecute individuals who support terror groups.
However, Turkish President Recep Tayyip Erdoğan warned on Wednesday that Stockholm must also do its part on the PKK terror group ahead of the NATO summit.
NATO leaders will meet in the Lithuanian capital Vilnius on July 11-12.
