As commissioner for defence and space, the former Lithuanian prime minister "will work on developing the European defence union and boosting our investment in industrial capacity," EU chief Ursula von der Leyen told reporters at the European Parliament in Strasbourg.

Faced with Russia's war on Ukraine, von der Leyen promised to name a designated defence commissioner as a key part of her new top team.

But while the position was originally billed as central to the EU's ambitions, there are doubts over how much power it will actually have.

Kubilius, a two-time prime minister of Lithuania and member of the European Parliament since 2019, has been a vocal supporter of Kyiv's fight to repel the Russia's invasion and a noted hawk towards both Moscow and Beijing.

Addressing the European Parliament ahead of von der Leyen's press conference, Kubilius argued that the EU needs "to radically ramp up production of our military industry and to integrate Ukraine's military industry with the European one.

"And we need to remove any red lines in the defence of Ukraine," he said.

Fluent in Russian, Kubilius was a leading light in Lithuania's drive for independence from the Soviet Union and not afraid to take on Moscow during his time as premier.

The mild-mannered physicist-turned-politician, who pursued an unpopular austerity drive while prime minister, sits with von der Leyen's centre-right European People's Party in parliament.

Until now, von der Leyen had been tight-lipped about what exactly the new defence job would entail.

One thing is sure -- the new defence commissioner is not an EU defence minister: the 27-nation bloc has no army of its own and is not planning to set up one any time soon.

Instead the main focus will be overseeing efforts to try to bolster the continent's defence sector, a major preoccupation since Russia's tanks rolled into Ukraine in 2022.

After years of underinvestment, Europe has struggled to ratchet up capacity and remains a long way behind Russia in the race to churn out arms.

While von der Leyen has estimated that the bloc will need to invest 500 billion euros ($550 billion) overall on defence over the next decade -- the figures on the table at an EU level are far below that.

According to diplomats, the questions swirling over the new job led EU powerhouses such as France and Poland to switch their priorities to obtaining other positions.

That means Kubilius could face a challenge carving out a niche in a turf war for influence in Brussels with some of the big names in the next commission.