But Stoltenberg said the meeting between him and representatives of Sweden and Turkey was productive and expressed his optimism about the prospect for Sweden to become a NATO member.

Turkish President Recep Tayyip Erdogan will meet Swedish Prime Minister Ulf Kristersson Monday in Vilnius, Lithuania, before the alliance’s summit next week.

According to Stoltenberg, Sweden has delivered on the commitments it made under the trilateral memorandum. Sweden has amended its constitution, introduced new anti-terrorist legislation, and removed restrictions on arms exports to Ankara.

Turkish Foreign Minister Hakan Fidan acknowledged Sweden's adjustments, but added countries that want to join NATO must take a firm stance in the fight against terrorism.

Swedish Foreign Minister Tobias Billstrom said Stockholm expects a positive outcome next week.