STOCKHOLM Prime Minister Ulf Kristersson said on Wednesday that Sweden still wanted to join NATO before or at its summit in Vilnius next month although it was not certain it would be able to do so by then.

Sweden and Finland abandoned decades of military non-alignment in the wake of Russia's invasion of Ukraine last year, seeking greater security by joining NATO. Finland became an alliance member in April but the process has been slower for Sweden.

Sweden has set its sights on joining at the alliance's July 11-12 summit and while it has strong support from other members including the United States, both Turkey and Hungary have so far held back from ratification.

"Sweden will become a NATO member," Kristersson said in an interview with public service broadcaster SVT.

"Nobody can promise it will happen specifically in Vilnius or right ahead of Vilnius, even if that has been our ambition all along. And that is an ambition we share with every other NATO country as well."

Turkey has said Sweden harbours members of what it considers terrorist groups - a charge Sweden denies - and has demanded their extradition as a step toward ratifying Swedish membership. It has also expressed outrage over anti-Turkish demonstrations held in the Nordic country.

Meanwhile, Sweden has said freedom of speech is firmly enshrined in its constitution and that it has lived up to all the requirements set out in an agreement with Turkey and Finland struck in Madrid a year ago.

Swedish and Turkish officials met on June 14 for what Sweden's chief negotiator characterised as good talks, and are due to hold another high level meeting in Brussels organised by NATO Secretary General Jens Stoltenberg before the Vilnius summit.

"We've also said that we respect that it is Turkey that makes Turkish decisions and it is good we now have another meeting ... and maybe we can address the odd question mark ahead of the Vilnius summit in that kind of conversation," Kristersson said.

(Reporting by Niklas Pollard; editing by Angus MacSwan)