"Our credibility towards our European partners and NATO allies is at stake," Bardella, 28, said at the Eurosatory arms trade show outside Paris, moderating the far right's historic hostility to the Atlantic alliance.

Bardella leads the National Rally (RN), whose three-time presidential candidate Marine Le Pen said in 2022 that if she were elected, France would quit NATO's integrated command in the name of "independence".

Her protege has said during the lightning campaign ahead of the June 30 first round of Macron's snap poll that he would not leave the structure as long as the war in Ukraine "is still going on".

Macron's camp made the RN's longtime admiration for Russia and its leader Vladimir Putin a key part of campaigning in 2022, when the centrist leader was re-elected against Le Pen but lost his parliamentary majority.

A massive loan the party received from a Russian bank in 2014, which it has since repaid, became a stick for its opponents to beat the RN with.

France's hard left has also long railed against NATO, joining in criticism in April when the country's only aircraft carrier, the Charles de Gaulle, came under the alliance's operational control for a two-week mission in the Mediterranean.