Sweden's Prime Minister Ulf Kristersson and Foreign Minister Tobias Billström are traveling to Washington today. Sweden's accession documentation will be officially deposited at the U.S. State Department, formally ending the process.
Sweden cleared the final hurdle to become the 32nd ally last week, after Hungary — the last holdout among member countries — held a parliamentary vote to approve the bid. The new president, Tamás Sulyok, signed it into law on Tuesday, immediately after being inaugurated.
Hungarian Prime Minister Viktor Orbán, who has maintained contact with Russian President Vladimir Putin in defiance of Western pressure, withheld approval of Sweden's bid for more than 600 days.
Turkey also slow-walked Sweden's accession on the grounds that it was not tough enough against the Kurdish minority living in the country.
Sweden's accession will be a strategic blow to Moscow. It turns the Baltic Sea into a NATO lake, making it much easier for the alliance to keep track of Russia's naval movements. Sweden also has a well-armed military and an advanced arms industry.
CORRECTION: This article has been updated to correct the date by which Sweden could join NATO; it could happen as early as Thursday.