(Bloomberg) -- Sweden and Finland submitted their applications to join the NATO military alliance in Brussels on Wednesday, marking the start of a process that would fortify Europe’s defenses in the event of Russian threats to the region.

“This is a good day at a critical moment for our security,” North Atlantic Treaty Organization Secretary General Jens Stoltenberg told reporters. “This is a historic moment which we should seize.”

The application will be assessed by all 30 NATO allies and requires unanimous agreement. Turkish President Recep Tayyip Erdogan on Monday signaled he wouldn’t allow the Nordic nations to join, alleging they support Kurdish militants his government regards as terrorists. 

Turkey is engaged in talks with Sweden and Finland, and NATO members say they’re confident the Turkish concerns can be overcome.

Finnish President Sauli Niinisto, who is traveling to Washington, D.C. on Thursday with Swedish Prime Minister Magdalena Andersson, said he’s “optimistic” Turkey’s stance can be “managed through discussions.”

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