The announcement comes a week ahead of a summit of NATO leaders in Lithuania that will be dominated by the Western military alliance's response to the conflict and Kyiv's push for membership.

"Honoured by NATO allies' decision to extend my term as secretary general until 1 October 2024," Stoltenberg, 64, said in a statement. "In a more dangerous world, our alliance is more important than ever."

NATO's 31 countries decided to extend the term of the former Norwegian prime minister -- at the helm of the alliance since 2014 -- after failing to agree an obvious replacement.

Others seen as potential candidates for the post of NATO secretary general, including Danish Prime Minister Mette Frederiksen and British Defence Minister Ben Wallace, had recently dropped out of contention.

Frederiksen appeared to meet the requirements of some European allies as a possible first female leader and by being from the European Union.

But NATO nations on the alliance's eastern flank were pushing for someone from their region to take the reins, to underscore a tougher stance on Russia.

Britain's Wallace put himself forward but numerous NATO allies wanted a former head of state or government in charge, and France insisted on someone from an EU country.

Stoltenberg, whose tenure was already extended for a year shortly after Russia launched its invasion of Ukraine in February 2022, has the strong backing of the United States and other key allies.

US President Joe Biden welcomed the extension and praised Stoltenberg's "steady leadership, experience, and judgement" in dealing with the epochal security challenges.

Ukrainian President Volodymyr Zelensky praised "his personal efforts to support Ukraine's Euro-Atlantic aspirations", after a phone call with the NATO chief.

- Fine line -

Stoltenberg has won plaudits for his cool-headed stewardship of the alliance at a time when the biggest armed conflict since World War II has roiled Europe and reinvigorated NATO.

That has involved maintaining stalwart support for Kyiv while also making sure the war does not spill over into a potential nuclear conflict between NATO members and Russia.

The summit in Vilnius will see Stoltenberg treading a fine line again as he seeks to bridge gaps between Ukraine's demand to join the alliance and the reluctance of the United States, its dominant power, to offer a clear timeline for that process.

Leaders will sign off on new defence plans and spending goals as the alliance undergoes it biggest overhaul in a generation in the face of Moscow's Ukraine war.

Stoltenberg will also try to push Turkish President Recep Tayyip Erdogan to drop his objections to Sweden's membership bid, made along with Finland in the wake of the Ukraine conflict.

Stoltenberg had insisted that he was not seeking to prolong his time in charge at NATO, though he left the door open for the allies to ask him to stay.

The extension will see Stoltenberg remain in charge during a July 2024 Washington summit marking the 75th anniversary of NATO's founding.

Some countries were hesitant about granting him a one-year extension, on concerns that choosing his successor would become intertwined with jostling for top EU jobs after European elections next June.

There are also worries that the run-up to the US elections in November 2024 could disrupt the search for a replacement.