France will increase the size of its nuclear arsenal and strengthen its deterrent, with an increasing risk of conflicts globally crossing the nuclear threshold, President Emmanuel Macron said on Monday.

"We are currently experiencing a period of geopolitical upheaval fraught with risk," Macron said in a speech delivered from a submarine base in Brittany, adding that a "hardening" of the French deterrence model was needed.

Unveiling the update to France's nuclear doctrine at a nuclear base on the Atlantic coast, Macron also said a "major" change would see more cooperation with European allies that have expressed interest, including Germany.

Germany but also Poland, the Netherlands, Belgium, and Denmark would be able to take part in French nuclear wargames, Macron said, although he made clear decision-making on nuclear strikes will remain solely in the hands of the French president.

The French leader added it would be possible to establish, under unspecified circumstances, strategic assets in other European countries that would be part of what he called a new "forward deterrence" doctrine.

Though France and Britain are both nuclear powers, most European countries rely primarily on the United States for deterring any potential adversaries — a decades-old pillar of transatlantic security.

But President Donald Trump's rapprochement with Russia on the Ukraine war and his harsher posture towards traditional allies have rattled European governments.