STOCKHOLM, (Reuters) – Finland and Sweden should reach an agreement over Turkey’s objections about the Nordic countries joining NATO’s 30-nation alliance. This was stated by Finland’s President on Tuesday.

Turkey stunned NATO allies Monday when it said that it will not support Sweden or Finland’s membership, after these two countries made the highly anticipated decision to accept the U.S. alliance.

“Statements by Turkey have changed very rapidly and became harder over the past few days,” said President Sauli Niinisto during a speech before Sweden’s parliament.

“But, I’m sure, that with constructive discussion, we can solve this problem.”

Niinisto stated that he had spoken by telephone to Turkish President Tayyip Turkey a month before and that the message was supportive of Finnish or Swedish membership in NATO.

Niinisto added that “But in his last week, he’s said ‘not favorable’.” We must continue to discuss this. I am optimistic.”

Turkey accuses Finland and Sweden of harboring terrorists.

Ann Linde, the Swedish Foreign Minister (NYSE:), stated on Saturday that PKK was a terrorist organization and Sweden, just like other European Union members, before she meets with her Turkish counterpart during talks at the NATO Berlin meeting.

Erdogan spoke at Monday’s news conference and stated that Turkey will oppose any NATO bids made by those who have imposed sanctions against it. Following the 2019 incursion of Syria into Turkey, Sweden and Finland have imposed arms export embargoes upon Turkey.

It remains to be determined how big of an obstacle Turkey’s objections are.

“They are aware that Sweden and Finland within the alliance is beneficial for the whole alliance and they do not anticipate blocking this,” Anna Wieslander (Director, Northern Europe), at the Atlantic Council’s security policy think tank said.

“But they’ll negotiate all the way.”