"We conveyed our message in very clear terms that the process will not move forward unless Turkey's security concerns are addressed through concrete steps and within a certain timetable," presidential spokesman Ibrahim Kalin told reporters after meeting Swedish and Finnish representatives in the capital Ankara.

NATO member Turkey has opposed the applications of Sweden and neighbouring Finland over what it considers leniency toward Kurdish militant groups.

Stockholm and Helsinki submitted their bids to join NATO last week, reversing decades of military non-alignment, after political and public support for membership soared following Russia's invasion of Ukraine.

But Turkey is throwing a spanner in the works as any membership must be unanimously approved by all NATO members.

Ankara accuses Stockholm in particular of providing safe haven for the outlawed Kurdistan Workers' Party (PKK), listed as a terror group by Turkey and its Western allies.

"They told us they understand Turkey's security concerns, but we'll see what steps they will take," Kalin said, adding that dialogue would continue.

Sweden has imposed embargoes on arms sales to Turkey since 2019 over Ankara's military offensive in Syria.

Kalin said on Wednesday he was seeing a "positive" attitude on the removal of sanctions in the defence industry.

"We don't think it is appropriate for allies to impose sanctions on each other, that would weaken the alliance and make enemies happy," he added.