Nato officially invited Finland and Sweden to join the alliance on Wednesday after weeks of negotiations.
This decision followed the signing of a memorandum of agreement between the Nordic countries and Turkey, bringing progress to the application process.
Earlier, when Finland and Sweden announced their intentions to join the alliance, Turkey had objected, citing security concerns that the Nordic countries hosted suspected Kurdish terrorists and limited arms exports to Turkey.
As a result of the agreement reached on Tuesday, Turkey has agreed to fully support both Finland's and Sweden's bids into the alliance.
Turkey claimed that it was intending to seek the extradition of 33 suspected terrorists from Finland and Sweden to Turkey, but Finnish President Sauli Niinistö denied any new extradition requests on Wednesday.
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Stoltenberg: "Good agreement"
"This is a good agreement for Turkey. It is a good agreement for Finland and Sweden. And it is a good agreement for Nato," said the alliance's secretary general, Jens Stoltenberg, at a Nato summit press conference in Madrid.
He noted that this was one of the fastest accession processes in the history of Nato.
"The countries applied in May, and now they have already been invited to become members…So far this is the fastest accession protocol ever," the top Nato official said.
While Finland and Sweden have been invited to join the alliance, they are not yet full members. However, Stoltenberg has previously said on a number of occasions that the countries' accession to the alliance would be swift.
Now, Finland and Sweden must prepare for the following steps in order to join the alliance. First, Nato experts and representatives will meet in Brussels to formally assess whether the countries are willing and able to meet the political, legal, and military requirements needed to join the alliance.
Then the countries will send a formal letter of intent saying that they formally accept the obligations of Nato.
Following this, the parliamentary process begins, in which member state legislatures will vote to admit Finland and Sweden into Nato. This process is expected to take about a year.
The final step, once all 30 member state legislatures vote on Finland's and Sweden's accession, will be to notify the US government, the depositary to the Washington Treaty—the framework treaty behind Nato.