Finnish president says he was 'astonished' that Turkey's President Erdogan suggested he might block Finland's NATO application

• Finland's president suggested that Turkey has changed its views on the Nordic nation joining NATO.
• Finnish President Sauli Niinistö said he was "astonished" by Turkey's possible opposition.

Finnish President Sauli Niinistö said on Sunday that he was "astonished" that Turkish President Recep Tayyip Erdogan suggested he might block Finland from joining NATO after Erdogan privately told him he would be fine with Finland joining the alliance.

"First, why I was astonished, because I had a telephone discussion with the president, Erdogan. That is about one month ago," Niinistö told CNN's Dana Bash on "State of the Union." "And then he said that they will estimate, well, positively our aim to apply for membership. And now it changed."

Finland signaled on Sunday that it would move to join NATO, a historic reversal of the Nordic nation's decades of neutrality. Sweden could soon join its neighbor in pursuing NATO accession in the coming days.

On Friday, Erdogan said Turkey did not hold "positive views" about either Finland or Sweden joining the North Atlantic Treaty Organization. Turkey's potential opposition is of paramount importance since it and NATO's other 29 members must unanimously accept any new applications.

Secretary of State Antony Blinken and NATO Secretary-General Jens Stoltenberg have also sought to downplay Erdogan's comments. Both Blinken and Stoltenberg suggested on Sunday that Turkey's concerns could be worked out.

"I'm confident that we will be able to address the concerns that Turkey has expressed in a way that doesn't delay the membership or the accession process," Stoltenberg told reporters, per Politico Europe. "My intention is still to have a quick and swift process."

Niinistö said he was "not worried about" Erdogan's views.

Erdogan claimed that "Scandinavian countries are guesthouses for terrorist organizations." His accusation is likely a reference to Sweden's support for the Kurdish-led Syrian Democratic Forces (SDF). The US has also supported the SDF, which has led to tensions between the two current NATO members.

The SDF has been the West's main partner in its fight against ISIS.