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

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

NATO countries made the call to extend the tenure 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, including Danish Prime Minister Mette Frederiksen and British Defence Minister Ben Wallace, had recently dropped out of contention.

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

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 -- who already had his tenure extended for a year shortly after Russia's invasion of Ukraine in February 2022 -- has the strong backing of the United States and other key allies.

- Fine line -

He has won plaudits for his cool-headed leadership of the alliance as 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 and Russia.

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

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 attack.

The NATO chief will also try to push Turkey's President Recep Tayyip Erdogan to drop his objections to Sweden's membership bid.

Stoltenberg had repeatedly insisted that he was not actively seeking to prolong his time in charge at NATO.

But he left the door open for the allies to ask him to stay.

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

Some countries were hesitant on granting a one-year extension for fear chosing his successor will 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.