Turkey blocked Sweden and Finland bids to join NATO
Sweden and Finland had a decades-old policy of neutrality that they now seem to want to change.
NATO needs a unanimous vote for new members.
The main reason given by Turkey is that those countries host Kurdish groups the Turkish government deems terrorists.
Diplomats from the two countries are going to Turkey to try diplomacy, but Erdogan publicly said they shouldn't bother to tire themselves, as Turkey won't accept counties that impose sanctions (export bans on Turkey... Sweden halted arms sales to Turkey after Turkish intervention in Syria 3 years ago) on Turkey, because then NATO would cease to be a security organization and start to be a place where reps of terrorist organizations are represented.