Nato Secretary-General Jens Stoltenberg says that Turkey has "legitimate concerns" over terrorism and other issues that need to be taken seriously.
Turkey has accused Finland and Sweden of supporting Kurdish militants and says it will not back the two Nordic nations joining Nato until they change their policies.
Speaking at a joint news conference with Finnish President Sauli Niinisto, Stoltenberg stressed that "no other Nato ally has suffered more terrorist attacks than Turkey" and pointed to its strategic geographic location with neighbours like Iraq and Syria.
"These are legitimate concerns. This is about terrorism, it's about weapons exports," Stoltenberg said. "We have to address the security concerns of all allies, including Turkish concerns about the terrorist group PKK."