Her decision came days ahead of a crucial meeting of defence ministers from Ukraine's allies and with Berlin under intense pressure to provide battle tanks to Kyiv.

Chancellor Olaf Scholz said he had a "clear idea" of who would succeed Lambrecht, adding that this would be announced "very quickly". But government sources told AFP no decision was expected on Monday.

Lambrecht, 57, said in a statement she had asked Scholz to relieve her of her duties.

"The months-long media focus on my person hardly allows for objective reporting and discussion about servicemen and women... and security policy decisions in the interest of the citizens of Germany," she said.

The politician from Scholz's Social Democrats (SPD) had faced criticism for months over what some see as Germany's wavering response to the conflict in Ukraine.

Patience for Lambrecht ran out when she posted a New Year's video on social media in which she lauded her "special experiences" as defence minister in 2022 against a backdrop of loud fireworks.

Leading German media blasted the tone-deaf message, with some commentators saying she was "no longer tenable as a minister".

Rumours had been swirling ever since that she was planning to hand in her resignation.

- Tanks for Ukraine -

Lambrecht's move comes days before the Ukraine Defence Contact Group, which coordinates arms supplies to Kyiv, is due to meet at the Ramstein Air Base in Germany.

The swap in defence minister at such a crucial time risks further dampening confidence in Berlin's ability to respond swiftly to Ukraine's needs.

The defence portfolio was always going to be daunting even before the war in Ukraine.

Lambrecht, who took office in December 2021, had been expected to address a litany of military equipment failures that had made the armed forces a laughing stock in Germany.

But Russia's invasion of Ukraine added urgency to her task, leaving her in charge of Germany's colossal plan to revive its ailing army with a special fund of 100 billion euros ($108 billion).

At the same time, the conflict also exposed a lack of understanding of the workings of modern warfare.

Even before Russia's offensive, Lambrecht was mocked in January 2022 for her announcement that Germany would send 5,000 helmets to Kyiv, where the Ukrainian government was seeking weapons to ward off Moscow.

She then came under fire in May for allowing her son to accompany her on a government helicopter on their way to a family vacation.

In the fateful video posted earlier this month, Lambrecht reflected on a year ending with "war raging in the middle of Europe".

To the backdrop of exploding fireworks during chaotic New Year's celebrations in Berlin, the minister said the war in Ukraine had led to "a lot of special experiences" and the chance for "many encounters with great and interesting people".

- Cabinet reshuffle? -

Names of senior SPD politicians are already circulating for Lambrecht's replacement, including Eva Hoegl, the parliamentary commissioner on armed forces.

Filling the post might also bring about a cabinet reshuffle that could shift Employment Minister Hubertus Heil to the defence portfolio.

However, the Bild daily reported that Heil was out of the running, along with SPD leader Lars Klingbeil and chancellery chief Wolfgang Schmidt.

Marie-Agnes Strack-Zimmermann of Scholz's junior coalition partner FDP, who is the chairman of the parliamentary defence commission, urged the chancellor to swiftly replace Lambrecht.

"I expect the Social Democrats to appoint a successor as soon as possible who is assertive vis-a-vis the ministry, who does not misuse the defence ministry for other political ambitions and, above all, who brings understanding and a heart for the soldiers," she told Funke media group.