Britain pledged to defend Sweden if the country came under attack, with Prime Ministers Boris Johnson and Magdalena Andersson signing a security assurance deal outside Stockholm on Wednesday.
Johnson is expected to make a similar defence commitment to Finland, where he will meet with President Sauli Niinisto later on the same day.
Sweden and Finland are currently considering whether to join NATO following Russia's invasion of Ukraine on 24 February.
The new agreement will “fortify northern Europe’s defenses, in the face of renewed threats,” Johnson said in a statement, adding it is “a symbol of the everlasting assurance between our nations".
“These are not a short-term stop-gap, but a long-term commitment to bolster military ties and global stability, and fortify Europe’s defenses for generations to come,” Johnson said in the statement. Finland shares a 1,340-kilometer land border with Russia.
The Kremlin has warned of “military and political repercussions” if Sweden and Finland decide to join NATO.
Should Sweden and Finland apply, there will be an interim period between the application and all 30 NATO members’ parliaments ratifying it. The two Nordic countries are expected to announce their positions on NATO membership in the coming days.
Johnson also offered to increase the deployments of British troops and military assets to the region during his visit.
He met with Andersson in Harpsund, the country retreat of Swedish prime ministers, which is located about 90 kilometres southwest of Stockholm.
The United Kingdom is already present in the Baltic Sea areas with the Joint Expeditionary Force, which consists of 10 Northern European nations: the UK, Sweden, Finland, Denmark, Estonia, Iceland, Latvia, Lithuania, the Netherlands
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