Swedish membership in NATO would boost national security and help stabilise the Nordic and Baltic regions, Foreign Minister Ann Linde said today, a day after neighbour Finland said it would seek to join the US-led military alliance without delay.

Russia's invasion of Ukraine has forced Sweden - and its closest military partner Finland - to publicly pick sides after remaining outside the Atlantic alliance since it was founded in 1949 to counter the Soviet Union in the Cold War.

Stockholm is widely expected to follow Helsinki's lead and could apply for entry to the 30-nation NATO as early as Monday.

Italy fully backs Finland, Sweden joining NATO - foreign minister

Italy will fully support NATO membership for Finland and Sweden, Foreign Minister Luigi DiMaio said today.

"We as Italy will be very happy to welcome these two countries in this great alliance that defends its member countries and... which has guaranteed peace for decades," Mr DiMaio told reporters in Berlin.

'Sweden would be a part of NATO's collective security'

"Swedish NATO membership would raise the threshold for military conflicts and thus have a conflict-preventing effect in northern Europe," Ms Linde told reporters as she presented the conclusions of an all-party security review which examined the pros and cons of NATO membership for Sweden.

"The most important consequence of Swedish membership of NATO would be that Sweden would be a part of NATO's collective security and included in security guarantees according to...Article 5."

Article 5 of NATO's founding treaty states that an attack on any NATO country should be seen as an attack on all.

While Sweden and Finland have close relations with NATO for years and regularly take part in exercises and meetings of its top brass, they are not covered by its security guarantee.

From Arctic to the Black Sea

Finland and Sweden joining NATO would redraw the geopolitical map of northern Europe and create a largely unbroken ribbon of member states facing Russia, stretching from the Arctic to the Black Sea.

Yesterday, Finland's president and prime minister said the country - which shares a 1,300km border and a difficult past with Russia - must apply to join the NATO military alliance "without delay".

Russia said Finland's bid was a hostile move that posed a threat to its security.

Moscow has previously spoken about potentially stationing nuclear-armed missiles in the Russian territory of Kaliningrad, sandwiched between NATO members Poland and Lithuania on the Baltic Sea, if Finland or Sweden joined the bloc.

"If Sweden chooses to seek NATO membership, there is a risk of a reaction from Russia," Defence Minister Peter Hultqvist said. "Let me state that, in such a case, we are prepared to deal with any counter-response."

On Sunday, Sweden's ruling Social Democrats will decide whether to formally approve joining NATO and are widely expected to drop decades of opposition to membership. Parliament will then debate security issues on Monday.

An application would have to be approved by all NATO countries and later, by Sweden's parliament.

NATO Secretary-General Jens Stoltenberg said yesterday that Finland would be "warmly welcomed" and promised a "smooth and swift" accession process, while the US government said it would support a membership bid by Finland and Sweden alike.