French President Emmanuel Macron has advocated a more coordinated European Union defence strategy in which France, the bloc's only post-Brexit nuclear power, and its arsenal would hold a central role.

Addressing military officers graduating in Paris on Friday, Macron set out his country's nuclear strategy in a bid to show leadership one week after nuclear-armed Britain officially exited the EU.

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Macron highlighted how France sees its nuclear weapons as a deterrent against attacks from belligerent foes, though he conceded France's nuclear might is diminished after its military scaled down its arsenal to less than 300 nuclear weapons.

But the speech aimed to project strength, as Macron refused to sign any treaty at this stage to further reduce the French arsenal, announced an increase in military spending and positioned himself as the driving force for a united EU - using France's military clout to make his point.

Macron also touted the French military's role in spots such as Africa's Sahel, where he has just pledged an additional 600 troops to battle fighters.

The central idea in the keynote speech, however, was that of a boosted Europe-wide role for the French nuclear arsenal in a more coordinated European defence policy.

Macron said the strategy would prevent Europe "confining itself to a spectator role" in an environment dominated by Russia, the United States and China.

"Europeans must collectively realise that, in the absence of a legal framework, they could quickly find themselves exposed to the resumption of a conventional, even nuclear, arms race on their soil," Macron warned.

His remarks come at a time when NATO allies, who would ordinarily look to the US for help in a nuclear standoff, worry about Washington's retreat from the multilateral stage.

This could create new tensions within NATO, where Macron ruffled feathers last year by saying the lack of US leadership is causing the "brain death" of the military alliance.

Last year, Russia and the US pulled out of the Intermediate Range Nuclear Forces (INF) treaty - dating from the era of the Soviet Union - and each blamed the other for its failure. Evoking the tearing-up of the INF treaty, Macron said he wanted the Europeans to propose their own "international arms control agenda together".

Friday's speech was part of Macron's long-running push for a stronger European defence, as US President Donald Trump has pulled away from European allies and admonished them to pay more for their own protection.

Macron explained his vision as "an offer of dialogue" and "service" to Europeans to assert their autonomy "in defence and arms control".