French President Emmanuel Macron warned Friday that European nations "cannot remain spectators" in the face of a potential nuclear arms race and urged them to push an "international arms control agenda".

"Europeans must realise collectively that in the absence of a legal framework, they could rapidly face a new race for conventional weapons, even nuclear weapons, on their own soil," Macron said in a speech laying out France's post-Brexit strategy for its nuclear arsenal.

He added that France had already reduced the number of its warheads to under 300, providing "the legitimacy to demand concrete moves from other nuclear powers toward global disarmament that is gradual, credible and can be verified".

After Brexit, France is the only nuclear power within EU borders, at a time when long-standing accords on limiting the growth of nuclear stockpiles appear increasingly at risk.

The United States has suggested it will not extend New START, an arms reduction treaty signed in 2010, and both Washington and Moscow have abandoned the Intermediate-Range Nuclear Forces (INF) Treaty.

Macron said France remains convinced that Europe's long-term security depends on a strong alliance with the US, its key partner in the NATO alliance.

"But our security also depends, inevitably, on a greater capacity for autonomous action by Europeans," he said in the speech to military officers in Paris.

As a result, European nations should be signatories of any new deal to limit the development of new intermediate-range weapons, Macron said.

"Let us be clear: if negotiations and a more comprehensive treaty are possible... Europeans must be stakeholders and signatories, because it's our territory" that is most at risk, he said.

Macron has already begun a costly modernisation of France's atomic arsenal, arguing in January 2018 that "deterrence is part of our history, part of our defence strategy, and will remain so."