Finland will officially become the 31st member of the North Atlantic Treaty Organization (NATO) on Tuesday, April 4, the Finnish president's office said on Monday.

Finnish President Sauli Niinisto, Foreign Minister Pekka Haavisto and Defense Minister Antti Kaikkonen will attend the accession ceremony at NATO Headquarters in Brussels, the office said in a press release.

On behalf of Finland, Haavisto will deposit its instrument of accession with the US State Department in Brussels on Tuesday. To mark the occasion, the country's flag will be hoisted outside NATO's headquarters.

Speaking ahead of the April 4-5 meeting of the foreign affairs ministers of the NATO member states in Brussels, the alliance's Secretary General, Jens Stoltenberg, said that "we have seen the fastest ratification process in NATO's modern history."

Along with Sweden, Finland handed in its official letter of application on May 18, 2022. Sweden's application has yet to be ratified by Turkiye and Hungary. "I look forward to also welcoming Sweden as a full member of the NATO family as soon as possible," Stoltenberg said, calling it a "top priority."