EXPLAINER: Why is Turkey wary of Nordic states' NATO bid?

Turkish President Recep Tayyip Erdogan has thrown a spanner in the works of Sweden and Finland’s historic decisions to seek NATO membership

ANKARA, Turkey -- Turkish President Recep Tayyip Erdogan has thrown a spanner in the works of Sweden and Finland’s historic decisions to seek NATO membership, declaring that he cannot allow them to join due to their alleged support of Kurdish militants and other groups that Ankara says threaten its national security.

NATO Secretary General Jens Stoltenberg has voiced confidence that the alliance will move to admit Sweden and Finland swiftly. But Erdogan's declaration suggests that the two Nordic countries’ path to membership could be anything but smooth.

Turkey’s approval is crucial because the military alliance makes its decisions by consensus. Any of its 30 member countries can veto a new member.

Erdogan’s government is expected to use the two countries’ membership bids as leverage for concessions and guarantees from its allies.