Sweden’s prime minister announced on Monday that Sweden would join Finland in seeking Nato membership in the wake of Russia’s invasion of Ukraine, a historic shift that comes after more than 200 years of military nonalignment in the Nordic country.

The move, which is likely to upset the government of Russian President Vladimir Putin, came after neighbouring Finland announced on Sunday that it too would seek to join the 30-country military alliance.

Prime Minister Magdalena Andersson called it “a historic change in our country’s security policy”, as she addressed lawmakers in the Swedish capital.

“We will inform Nato that we want to become a member of the alliance,” she said. “Sweden needs formal security guarantees that come with membership in Nato.”

Andersson added that Sweden was acting together with Finland.

The announcement came after a debate in the Riksdagen, or parliament, earlier on Monday showed that there was huge support for joining Nato. Out of Sweden’s eight parties, only two smaller left-leaning parties opposed it.

On Sunday, the Swedish Social Democrats broke with the party’s long-standing position that Sweden must remain nonaligned, paving the way for a clear majority for Nato membership in the parliament.

Public opinion in both Nordic countries was firmly against joining Nato before the Russian invasion of Ukraine on February 24, but support for Nato membership surged quickly in both nations after that.

“The Swedish government’s intent is to apply for Nato membership. A historic day for Sweden,” Foreign Minister Ann Linde wrote on Twitter. “With a broad support from political parties in the parliament, the conclusion is that Sweden will stand stronger together with allies in Nato.”

Once a regional military power, Sweden has avoided military alliances since the end of the Napoleonic Wars. Like Finland it remained neutral throughout the Cold War, but formed closer relations with Nato after the 1991 Soviet collapse.

After the Russian invasion of Ukraine, the governments in Finland and Sweden responded by swiftly initiating discussions across political parties about Nato membership and reaching out to the US, Britain, Germany and other Nato countries for their support.

The Kremlin, however, has repeatedly warned the move would have destabilising consequences for security in Europe.

Russian President Vladimir Putin said on Monday that Moscow “does not have a problem” with Sweden or Finland as they apply for Nato membership, but that “the expansion of military infrastructure onto this territory will of course give rise to our reaction in response.”

In Helsinki, Senate Republican leader Mitch McConnell said on Monday that there is “very significant” support in Congress and that he expects swift ratification. He said he hoped a vote could be held before the August recess.

In the Swedish Parliament, only the small Left and Green parties objected to seeking Nato membership.

Andersson said Sweden would refuse nuclear weapons or permanent Nato bases on its soil — similar conditions as neighbouring Norway and Denmark insisted on when the alliance was formed after World War II.

Though Nato officials have expressed hopes for a quick ratification process, all 30 current Nato members must agree to let Finland and Sweden in the door. Turkey voiced some objections last week, accusing the two countries of supporting Kurdish militants and others whom Turkey considers to be terrorists.

Swedish Defence Minister Peter Hultqvist told public broadcaster SVT that a Swedish delegation would be sent to Ankara to discuss the issue.