After the signing on Tuesday, the protocol must be ratified by all 30 allied parliaments to allow Sweden and Finland to become part of the transatlantic defence alliance.
The NATO accession protocol for Sweden and Finland will be signed on Tuesday, Secretary-General Jens Stoltenberg has said.
"We are going to formally sign the accession protocol on Tuesday, with the presence of the foreign ministers of Sweden and Finland, but the decision has already been made," Stoltenberg said at a press conference as NATO's Madrid Summit ended on Thursday.
After the signing, the protocol must be ratified by all 30 allied parliaments to allow the Nordic countries to become part of the transatlantic defence alliance.
The Nordic countries were officially invited to the alliance following a trilateral memorandum signed by Türkiye, Finland and Sweden on Tuesday. The memorandum addresses Türkiye's concerns, including arms exports and the fight against terrorism.
Regarding Russia's aggression in Ukraine, Stoltenberg said: "(President Vladimir) Putin has to withdraw his forces and end this war immediately."
"NATO has to provide support to Ukraine, but it also has a co-responsibility to prevent an escalation beyond Ukraine," he said, closing the summit with a message that the allies are prepared to “protect every inch of NATO territory” and fully back Ukraine.
"If this escalates to a war between NATO and Russia, we will see suffering, damage and death on a scale we haven't seen yet," the NATO chief added.
Stoltenberg said the three-day summit in Madrid featured several “transformative” decisions.
Besides pledging more aid for Kiev and extending formal invitation to Sweden and Finland, the allies agreed to boost their rapid response forces in Eastern Europe from 40,000 to 300,000 and approved a new list of top security priorities for the next decade, among other decisions.
“We face the most serious security situation in decades, but we are rising to the challenge with unity and resolve,” Stoltenberg said.