Finland and Sweden on Wednesday formally submitted applications to join the NATO trans-Atlantic military alliance, marking a radical change in the Nordic countries' security policy in the wake of Russia's invasion of Ukraine.
North Atlantic Treaty Organization Secretary General Jens Stoltenberg welcomed the historic move at a ceremony in Brussels. "You are our closest partners, and your membership in NATO would increase our shared security."
U.S. President Joe Biden also said in a statement that he "strongly" supports the applications and looks forward to working with NATO allies to "quickly bring Finland and Sweden into the strongest defensive alliance in history."
All 30 NATO countries must ratify an application to approve a new member. The process could be prolonged as Turkey has expressed some hesitation over the move.
If the applications are approved, NATO's border with Russia would roughly double in length and almost certainly change the geopolitical landscape in Europe.
Sweden has not participated in a war since the Napoleonic Wars in the 19th century, when it lost territory, and has preferred neutral mediation roles in international disputes. Finland, which has a 1,300-kilometer border with Russia, adopted neutrality after fighting with the Soviet Union during World War II and losing some of its territory.
As Russia's assault on Ukraine continues, Swedish Prime Minister Magdalena Andersson and Finnish President Sauli Niinisto stressed that close cooperation between the two countries is extremely important, telling a joint press conference on Tuesday they share common history, tradition, values and culture.
Moscow has strongly opposed Finland and Sweden joining the organization, and Russian President Vladimir Putin has warned he will take countermeasures if either of the two countries hosts NATO military facilities.
While the applications for NATO membership are being considered, the United States will work with Finland and Sweden to "remain vigilant against any threats to our shared security, and to deter and confront aggression or the threat of aggression," Biden said.
He also reaffirmed that the U.S. commitment to NATO's collective defense principle is "ironclad."
The Biden administration has provided security assistance to help Ukraine, a non-NATO member, defend itself against Russia's aggression. But it has not put U.S. troops on the ground in Ukraine amid fears of being drawn into a direct conflict with nuclear-armed Russia.