Parliaments in all 30 members of the military alliance must formally ratify Finland and Sweden before they can be admitted. Turkey and Hungary are the only two NATO members not to have done this.

Turkey has suggested it could greenlight Finland's bid to join without accepting Sweden into the alliance.

"So the main question is not whether Finland and Sweden are ratified together. The main question is that they are both ratified as full members as soon as possible," Stoltenberg said ahead of a meeting of NATO allies.

"I'm confident that both will be full members and we are working hard to get both ratified as soon as possible," the NATO secretary general added.

Meanwhile, German Foreign Minister Annalena Baerbock said during a visit to Stockholm on Tuesday that the two countries should be admitted before NATO's summit in July in Vilnius.

"Sweden and Finland fulfil the conditions that we have agreed upon in Madrid so it is very important for NATO as a whole that Sweden and Finland can join before the next summit", she told reporters.

Leaders from the two Nordic countries have insisted on their desire to join together.

But a majority of Finns said in a poll this month that they wanted to go ahead and join NATO if Sweden's membership was delayed.

- 'Unfortunate' -

Joining separately would be "unfortunate", Swedish Prime Minister Ulf Kristersson said Tuesday.

"But I have respect for Finland, I know what Finland wants. And only Turkey makes decisions for Turkey", he told reporters.

Finland, which shares a long border with Russia, and Sweden dropped decades of military non-alignment and applied to join NATO in May last year in response to Moscow's invasion of Ukraine.

Turkey has so far refused to ratify the two countries' membership bids, primarily because of Sweden's refusal to extradite dozens of suspects that Ankara links to outlawed Kurdish fighters and a failed 2016 coup attempt.

Ankara reacted with fury to a decision by the Swedish police to allow a protest at which a far-right extremist burned a copy of the Koran outside the Turkish embassy in Stockholm last month.

Turkish President Recep Tayyip Erdogan has drawn a clear distinction between the positions taken by Sweden and Finland in the past few months and said "we can give a different response" to Helsinki.

Turkey's legislative and presidential elections in May could delay the ratification process.

Last week's devastating quakes in Turkey and Syria could, however, see the elections postponed.

Sweden and Finland are already heavily integrated into NATO thanks to their status as invited members.

They have also received security guarantees from a number of member states, including the US and Britain, pending their full membership.

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