"Turkey has confirmed that we have done what we said we would do, but it also says that it wants things that we can't, that we don't want to, give it," Ulf Kristersson said during a security conference also attended by NATO chief Jens Stoltenberg.

"We are convinced that Turkey will make a decision, we just don't know when," he said, adding that it will depend on internal politics inside Turkey as well as "Sweden's capacity to show its seriousness."

Sweden and Finland broke with decades of military non-alignment and applied to join the US-led defence alliance in response to Russia's February invasion of Ukraine.

But Turkey has refused to approve their bid until the two countries take steps, including joining Turkey's fight against banned Kurdish militants.

Most of Turkey's demands have involved Sweden because of its more robust ties with the Kurdish diaspora.

Finland's foreign minister said that the country would join NATO at the same time as its neighbour.

"Finland is not in such a rush to join NATO that we can't wait until Sweden gets the green light," Pekka Haavisto, told reporters at Sunday's conference.

NATO Secretary General Stoltenberg said he expects both countries will be able to join the military alliance as early as this year, while admitting the decision depends on the Turkish and Hungarian parliaments.

Among the 30 NATO members, only Hungary and Turkey are yet to green-light the two Nordic applications.

But Hungary's Prime Minister Viktor Orban has said parliament will soon approve both Finland and Sweden's accession bids, leaving Turkey the main holdout.

"I expect (that accession will take place in 2023), but I will not guarantee the exact date, because it is of course a sovereign decision of the Turkish and Hungarian parliaments, (which) have not yet ratified the agreement," Stoltenberg said in an interview with AFP.

Finland and Sweden "are clearly committed to long-term cooperation with Turkey," and "the time has come to finalise the accession process and to ratify the accession protocol," he added.

In late December, Turkey praised Sweden for responding to its security concerns but stressed more was needed to win Ankara's full backing for Stockholm's stalled NATO membership bid.