Macron said Monday France would expand its atomic arsenal and could deploy nuclear-armed aircraft to allied countries for the first time, in a potential major shift for Europe's defence at a time of strained ties with the United States.

"France's nuclear deterrent already contributes to the security of the alliance, and we welcome the initiative by President Macron to enhance deterrence further," a NATO official told AFP, speaking on condition of anonymity.

"We welcome the opportunity to expand consultation on nuclear issues with France in order to ensure a coherent, coordinated approach."

Macron updated France's nuclear doctrine as Russia's war against Ukraine grinds into a fifth year and NATO allies worry whether Washington's commitment to Europe is wavering.

Reassurances from US officials that the American deterrent would continue to cover Europe under the NATO alliance have done little to quell European fears of fickleness under US President Donald Trump.

Macron announced that eight European countries, including Britain, Germany, Poland and Sweden, had agreed to participate in what he called a "forward" nuclear deterrence scheme.

NATO's nuclear deterrence relies on the United States, while France remains independent of the alliance's nuclear planning group.

Macron said the efforts by France -- the only European Union country with nuclear weapons, and the only on the continent besides Britain -- would complement NATO's mission.

NATO chief Mark Rutte insisted earlier this month that "nobody" was pushing to replace the US nuclear umbrella in Europe.