Finland must seek immediate membership in NATO, leaders of the Nordic nation said on Thursday, moving to end seven decades outside the Western military bloc in response to Russia’s war in Ukraine.

Finland’s entry would add significant combat power to the alliance while also deepening the East-West divisions that have consumed Europe since Russia’s Feb. 24 invasion. Neighboring Sweden is expected to announce its own NATO bid soon.

Moscow said that Finnish accession, which would add hundreds of miles to NATO’s shared border with Russia, would threaten its security. Kremlin spokesman Dmitry Peskov said Finnish membership could require new measures by Russia to “balance the situation.”

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