Finland's President Sauli Niinisto confirmed Sunday that his country would apply for membership of the NATO military alliance, in a historic policy shift prompted by Russia's invasion of Ukraine and added that he would discuss the issue with Turkey.

Finland is ready to talk with Ankara on problems raised by President Recep Tayyip Erdoğan on NATO membership, Niinisto underlined after Turkey had voiced reservations about Finland and Sweden's NATO membership bid due to the two countries' support of the PKK terrorist organization, which poses serious national security threats to Turkey and is responsible for the death of innumerable Turkish citizens and troops.

Moscow, which shares a 1,300-kilometer (800-mile) border with Finland, has said it would be a mistake for Helsinki to join the transatlantic alliance and that it would harm bilateral ties.

Sweden is also expected to follow suit as public support for membership has grown amid security concerns.

Sunday's announcement comes after Niinisto and Prime Minister Sanna Marin said on Thursday they both favored NATO (North Atlantic Treaty Organization) membership, giving a green light for the country to apply.

"Today, we, the president and the government's foreign policy committee, have together decided that Finland ... will apply for NATO membership," Niinisto told reporters in the presidential palace in Helsinki.

Niinisto called Russian President Vladimir Putin on Saturday to tell him of Finland's plans to join the alliance. Putin said such a move would hurt Russian-Finnish relations.

"I, or Finland, are not known to sneak around and quietly disappear behind a corner. It is better to say it straight what already has been said, also to the concerned party and that is what I wanted to do," he said about his call on Sunday.

U.S. President Joe Biden held a joint call Friday with both Niinisto and Andersson where, according to a White House statement, he "underscored his support for NATO’s Open Door policy and for the right of Finland and Sweden to decide their own future, foreign policy and security arrangements."

The U.S. is also working with Turkey on the NATO membership of the two nations, the White House said, after President Recep Tayyip Erdoğan voiced Ankara's objection over Helsinki and Stockholm's welcoming stance toward the PKK and other terrorist groups.