Finland and Sweden must subsequently submit their letters of approval to the U.S. State Department, which is the alliance's treaty-appointed depositary.
On Monday, the 30 members of the North Atlantic Treaty Organization (NATO) signed accession protocols for Sweden and Finland, starting the process to admit the two Nordic countries into the alliance that perhaps poses a grave challenge to global security.
"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," NATO Secretary Jens Stoltenberg after the signing ceremony in which Finland's Foreign Minister Pekka Haavisto and Sweden's Foreign Minister Ann Linde took part.
NATO's 30 members formally invited Finland and Sweden to join their alliance at the NATO Summit held last week in Madrid, Spain, only seven weeks after both countries handed their applications in response to the Russia-Ukraine conflict.
The accession process was initially blocked by Turkey, a NATO member that raised concerns over the fight against terrorism. After signing a memorandum of understanding (MOU) with Finland and Sweden, Turkey lifted its veto ahead of the NATO Madrid summit.
The next step is for the parliaments of all 30 NATO members to ratify Sweden and Finland's accession to NATO, according to their own national procedures.
After the parliaments of Finland and Sweden ratify their countries' accession to the alliance, the new members must submit their letters of approval to the U.S. State Department, which is the alliance's treaty-appointed depositary.
The last accession was ratified within a year, said Stoltenberg, but since Sweden's and Finland's accession process has been sped up since the beginning, this could go faster.