Swedish Prime Minister Ulf Kristersson speaks after a presentation of Sweden's NATO Instruments of Accession in the Benjamin Franklin Room at the State Department, March 7, 2024, in Washington. (PHOTO / AP)

WASHINGTON/STOCKHOLM - Sweden joined NATO in Washington on Thursday, two years after Russia's military operation in Ukraine forced it to rethink its national security policy and conclude that support for the alliance was the Scandinavian nation's best guarantee of safety.

Swedish Prime Minister Ulf Kristersson handed over the final documentation to the US government on Thursday, the last step in a drawn-out process to secure the backing of all members to join the military alliance.

"Good things come to those who wait," US Secretary of State Antony Blinken said as he received Sweden's accession documents from Kristersson.

For NATO, the accessions of Sweden and Finland - which shares a 1,340-km border with Russia - are the most significant additions in decades.

Sweden adds cutting-edge submarines and a sizable fleet of domestically produced Gripen fighter jets to NATO forces, and is a crucial link between the Atlantic and Baltic

"Sweden is a safer country today than we were yesterday. We have allies. We have backing," Kristersson said in an address to the Swedish nation from Washington. "We have taken out an insurance in the Western defence alliance."

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US President Joe Biden, in a statement, said the addition of Sweden made NATO "more united, determined, and dynamic than ever," adding that the accession of Sweden and Finland to the alliance meant the addition of "two highly capable militaries."

Sweden adds cutting-edge submarines and a sizable fleet of domestically produced Gripen fighter jets to NATO forces, and is a crucial link between the Atlantic and Baltic.

"Sweden’s accession makes NATO stronger, Sweden safer and the whole Alliance more secure," NATO Secretary General Jens Stoltenberg said in a statement.

"Joining NATO is really like buying insurance, at least as long as the United States is actually willing to be the insurance provider," said Barbara Kunz, a researcher at defense think tank SIPRI.

While Stockholm has been drawing ever closer to NATO over the last two decades, membership marks a clear break with the past, when for more than 200 years, Sweden avoided military alliances and adopted a neutral stance in times of war.

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As recently as 2021, its defense minister had rejected NATO membership, only for the then-Social Democrat government to apply, alongside neighbor Finland, just a few months later.

While Finland joined the alliance last year, Sweden was kept waiting as Türkiye and Hungary, which both have cordial relations with Russia, delayed ratifying Sweden's accession.

Türkiye approved Sweden's application in January.

Hungary delayed its decision on Sweden's accession until Kristersson made a goodwill visit to Budapest on Feb. 23, where the two countries agreed a fighter jet deal.