Finland may give security reassurances to Turkey regarding the PKK terrorist group’s activities in the country, Finnish Foreign Minister Pekka Haavisto said Sunday, as Ankara says it will not approve the two Nordic countries' NATO membership over their support for terrorist groups.

Haavisto told a live broadcast that Finland would reassure Ankara that they would start monitoring the PKK’s activities in a closer manner.

"Since the PKK is recognized as a terrorist group in Europe, we need to undertake the responsibility to prevent terrorist activities in Finland as well," the top diplomat said.

Noting that negotiations with Turkey would continue at the diplomatic level, Haavisto said he expects them to last several weeks.

"I am optimistic about the solution of the problems but this is not a problem," he added.

He continued by saying that Turkish and Finnish presidents touched upon Finland’s fight against terrorism in their phone call on Saturday.

Sweden and Finland formally applied to join NATO on Wednesday – a decision spurred by Russia's war on Ukraine, which began in February. But Turkey, a longstanding member of the alliance, has voiced objections to the membership bids, criticizing the countries for tolerating and even supporting terrorist groups.

President Recep Tayyip Erdoğan has placed an obstacle to Sweden and Finland joining the alliance. He accuses Stockholm, and to a lesser extent Helsinki, of supporting the PKK terrorist group and other groups that Ankara views as terrorists and a threat to national security.

Turkey, which has the second-largest army in NATO, also accuses the two Nordic countries of imposing restrictions on exports of defense industry equipment to Turkey and of failing to extradite suspects wanted by Turkish authorities.

In its more than 40-year terror campaign against Turkey, the PKK – listed as a terrorist organization by Turkey, the United States and the European Union – has been responsible for the deaths of over 40,000 people.