The alliance is expected to announce increased troop numbers in at its eastern borders, as well as more aid for Ukraine. Leaders from Asia and Oceania were also invited to address concerns about rising Chinese influence.

At the summit in Spain, leaders say they want to send a message to Russia, as NATO chief Jens Stoltenberg says Moscow's war in Ukraine presents the "biggest challenge" in the alliance's history.

Russian President Vladimir Putin said there will be "some tension" with Sweden and Finland if they join NATO. The two countries were invited to join the alliance on Wednesday.

In an interview with DW's Conflict Zone, Russian former Duma MP Ilya Ponomarev said Vladimir Putin's war aims go way beyond Ukraine. He argues that it is NATO in the Russian president's sights.

The Turkish veto against the Swedish and Finnish NATO accession was only lifted last month. But President Erdogan has repeated his threats of blocking the bids.

Foreign Minister Mevlut Cavusoglu slammed Finland and Sweden for allowing "terror propaganda" as the two countries await Ankara's permission to join NATO.

Foreign Minister Mevlut Cavusoglu slammed Finland and Sweden for allowing "terror propaganda" as the two countries await Ankara's permission to join NATO.

Chancellor Olaf Scholz said he was confident Finland and Sweden's NATO accession would progress rapidly. Sweden's Magdalena Andersson said the war in Ukraine had prompted major changes in Stockholm and Berlin alike.

Serbia's president has called on NATO peacekeepers to "do their job" in protecting the Serb minority in the breakaway province. The West fears that Russia is trying to encourage Belgrade to destabilize the region.

Envoys of the three countries were meeting for the first time since their key agreement in June. Ankara's opposition has continued to work as an obstacle for Finnish and Swedish NATO accession.

The NATO chief told a German newspaper that Russia and China have big plans for the polar region that could further spike geopolitical tensions. Washington is set to appoint its first Arctic ambassador.

As at US-led meeting in Germany, supporters of Ukraine were seeking donations for winter equipment as the conflict grinds on. Western powers praised military gains, but warned more aid was needed.