NATO has formally begun the process of Sweden and Finland joining the alliance, its secretary general has said.
NATO members signed the protocols of accession on Tuesday, in what Jens Stoltenberg labeled an "historic moment."
It comes after the NATO summit in Madrid last week where allied leaders agreed to invite Finland and Sweden to join the alliance.
"This is truly an historic moment. For Finland, for Sweden, for NATO and for our shared security," Stoltenberg said.
"This is a good day for Finland and Sweden, and a good day for NATO. With 32 nations around the table, we will be even stronger and our people will be even safer, as we face the biggest security crisis in decades," he added.
He said that NATO's door remains open to democracies in European that are "ready and willing to contribute to our shared security."
Some background: Finland and Sweden ended their decades of neutrality when they applied to join NATO following Russia's invasion of Ukraine, which was met by some opposition from Turkish President Recep Tayyip Erdogan, who accused them of housing Kurdish "terrorist organizations."
Last week, Turkey dropped its opposition after a joint memorandum was signed between the three countries, underscoring their commitment to fully support each other against threats to their security.