The security concerns of all NATO allies need to be addressed, the bloc’s chief Jens Stoltenberg said in a phone call with President Recep Tayyip Erdoğan on Saturday.

"Spoke with President @RTErdogan of our valued Ally #Turkey on the importance of #NATO’s Open Door and the membership applications by #Finland & #Sweden. We agree that the security concerns of all Allies must be taken into account and talks need to continue to find a solution," Stoltenberg said on Twitter.

Meanwhile, the president said unless Sweden and Finland "clearly show" that they will stand in solidarity with Turkey on fundamental issues, especially the fight against terrorism, Ankara will not approach their NATO membership bid positively.

Erdoğan informed Jens Stoltenberg that Turkey "sincerely supports" NATO's open-door policy, but the issue regarding Sweden and Finland's membership requests is "related to these countries' attitude toward Turkey's vital and national security interests," the Presidency's Directorate of Communications said in a statement.

Turkey last week said it would not view the applications of Finland and Sweden positively, mainly citing their history of supporting terrorist organizations, including the PKK and its Syrian wing, the YPG. In response to a Turkish operation against the PKK’s Syrian wing, the YPG in 2019, Sweden and Finland, among others, imposed restrictions on arms exports to Turkey. Over the last five years, both Sweden and Finland have failed to agree to Ankara's requests for the extradition of dozens of terrorists, including members of the PKK and the Gülenist Terrorist Group (FETÖ), the group behind the 2016 defeated coup in Turkey.

Moscow's invasion of Ukraine on Feb. 24 has swung political and public opinion in Finland and neighboring Sweden in favor of NATO membership as a possible deterrent against any future Russian aggression.

Sweden and Finland formally submitted applications for NATO membership to Secretary-General Jens Stoltenberg in an online video ceremony earlier on Wednesday. Stoltenberg said the alliance would assess the membership bid as quickly as possible, but stressed that the security interests of all allies "have to be taken into account," referring to Turkey's objections.

All 30 members of the alliance must agree before any new members can join.