Finland on Sunday officially announced its intention to join the NATO alliance, as Russia’s invasion of Ukraine dramatically shifts security considerations in Europe and ends decades of the Nordic nation’s military nonalignment.

Speaking at a news conference in Helsinki alongside the country’s Prime Minister Sanna Marin, Finnish President Sauli Niinisto described it as a “historic day.”

The decision still needs to be ratified by Finland’s parliament — but that is considered largely a formality.

It represents a seminal shift in military thinking in northern Europe following Russian President Vladimir Putin’s invasion of Ukraine. Amid threats from Moscow over NATO’s eastern expansion, Finland, which shares more than 800 miles of border with Russia, had held back from joining the 30-country military alliance since it was formed in 1949.

But since Russian tanks rolled into Ukraine in late February, support for joining NATO has surged among the Finnish public.

“Finland will maximize its security,” Niinisto said. Marin described it as an “important decision.”

“In Finland we still have the parliamentary process ahead of us, but I trust the Parliament will debate this historic decision with determination and responsibility,” she said.

The announcement came as NATO foreign ministers met in Berlin to discuss Finland and Sweden’s path to membership. Sweden, which has been closely coordinating with Helsinki on its decision on whether to join the military alliance, is expected to follow suit.

Finland’s leaders said Thursday that the countries should join NATO without delay, but the formal decision came Sunday after the president and a committee on foreign and security policy finalized a report on Finland’s accession to the alliance. The report will be submitted to Parliament on Monday.

NATO requires unanimity on the approval of new members, and Turkey has expressed skepticism over Finland and Sweden joining the alliance.

U.S. officials are hoping to smooth out differences within the alliance following Turkish President Recep Tayyip Erdogan’s pointed criticism of Sweden and Finland as “home to many terrorist organizations.”

The comments, referring mainly to the Kurdistan Workers’ Party, a militant organization known as the PKK, were seen as a threat by Turkey to veto any NATO expansion.

Hope that a compromise could be brokered emerged Saturday after an Erdogan adviser told Reuters: “We are not closing the door. But we are basically raising this issue as a matter of national security for Turkey.”

And in Berlin on Sunday, officials from other NATO countries expressed optimism that the process would move ahead.

German Foreign Minister Annalena Baerbock said that the two countries could join “very quickly” if they took that decision.

“Our doors are more than open and if their parliaments and their societies are going to decide to join NATO, this will make us even stronger,” she said. Germany is prepared to do everything it can for a “quick ratification process,” she added.

During the Berlin meeting, Secretary of State Antony Blinken also met with Ukrainian Foreign Minister Dmytro Kuleba to discuss military aid for Ukraine and the continuation of food exports to the developing world.

“More weapons and other aid is on the way to Ukraine,” Kuleba tweeted after the meeting. “We agreed to work closely together to ensure that Ukrainian food exports reach consumers in Africa and Asia.”

The State Department said Blinken discussed “details regarding the latest tranche of U.S. security assistance to bolster Ukraine’s defenses” and potential solutions to exporting Ukraine’s grain to international markets. The ongoing fighting in Ukraine, a major food exporter, has been linked to rising food prices and inflation in the developing world.

President Biden is expected to sign a $40 billion security package for Ukraine in coming days after passage in the Senate.