NATO Secretary-General Jens Stoltenberg (Photo: AFP/VNA)

He said he spoke to Turkish President Recep Tayyip Erdogan and they agreed to convene a high-level meeting in Brussels before the Summit.

That meeting will include foreign ministers, intelligence heads, and national security advisors, Stoltenberg said.

Sweden and Finland applied to join NATO last year after Russia launched its military campaign in Ukraine, but their accessions need to be ratified by all 30 NATO members. Finland has been accepted, but Sweden is still waiting for approval from Hungary and Turkey.