NATO leaders are gathering in Lithuania for a crucial summit that could shape the direction of the war in Ukraine and the future of the Western alliance.

The 31 allies hope to show Russia they have the resolve to support Ukraine militarily for the long term. They arrive with a welcome boost after Turkey dropped its objections to Sweden joining the alliance. But there remains disagreement over what to say about Ukraine's own ambitions of future membership.

Jens Stoltenberg, the Nato secretary general, said no final decision has been made on the language of the final communiqué, but added that he is absolutely certain that they will have unity and a strong message on Ukraine.

Over their two-day meeting, Nato leaders are expected to agree on new plans to deter and defend the alliance against future Russian aggression by beefing up their forces in the east.