HELSINKI/BRUSSELS, April 4 (Reuters) - Finland will become a member of NATO on Tuesday, completing a historic security policy shift triggered by Russia's invasion of Ukraine, while neighbour Sweden is kept in the waiting room. "It will be a good day for Finland's security, for Nordic security and for NATO as a whole," NATO Secretary-General Jens Stoltenberg told reporters on Monday. Sweden underwent a similar transformation in defence thinking and Stockholm and Helsinki applied together last year to join NATO. Moscow said on Monday it would strengthen its military capacity in its western and northwestern regions in response to Finland joining NATO. Stoltenberg said he was "absolutely confident" that Sweden will become a NATO member.

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