Abandoning their long established non-alignment policy after Russia invaded Ukraine, Finland and Sweden on Wednesday submitted a joint application for NATO membership.

But Erdogan is threatening to block the bid, singling out Sweden as "a complete terror focus, a complete terror haven," in a video broadcast he tweeted on Thursday.

"We will continue this policy in a determined fashion and we told relevant parties that we will say 'no' to Finland and Sweden joining NATO," the Turkish leader said in one excerpt of the video from his chat with young people.

The United States is "confident" that Turkey's concerns over accession to NATO by Finland and Sweden can be overcome, a top advisor to President Joe Biden said Wednesday.

"We're confident that at the end of the day Finland and Sweden" will enter NATO and "that Turkey's concerns can be addressed," National Security Advisor Jake Sullivan said.