BRUSSELS (AP) — NATO Secretary-General Jens Stoltenberg said Wednesday that Finland, Sweden have officially applied to join the world’s biggest military alliance, a move driven by security concerns over Russia’s war in Ukraine.

“I warmly welcome the requests by Finland and Sweden to join NATO. You are our closest partners,” Stoltenberg told reporters after a receiving their application letters from the two Nordic countries’ ambassadors.

The application must now be weighed by the 30 member countries. That process is expected to take about two weeks, although Turkish President Recep Tayyip Erdogan has expressed reservations about Finland and Sweden joining.

If his objections are overcome, and accession talks go as well as expected, the two could become members within a few months. The process usually takes eight to 12 months, but NATO wants to move quickly given the threat from Russia hanging over the Nordic countries’ heads.

Canada, for example, says that it expects to ratify their accession protocol in just a few days.

Public opinion in Finland and Sweden has shifted massively in favor of membership since Russia invaded Ukraine on Feb. 24.

Finland and Sweden are NATO’s closest partners. They have functioning democracies, well-funded armed forces and contribute to the alliance’s military operations and air policing. Any obstacles they face will merely be of a technical, or possibly political nature.

Follow the AP’s coverage of the war at https://apnews.com/hub/russia-ukraine