"Let us not delude ourselves," Macron said in his New Year's address to the French armed forces.

"This conflict will not end tomorrow or the day after," Macron said, speaking as Trump was sworn in and as the third anniversary of Russia's war against Ukraine approached next month.

Trump promised over the summer to end Russia's war against Ukraine "in 24 hours", although he did not explain how he planned to do that, before more recently suggesting a timeline of several months.

Speaking in Cesson-Sevigne in northwestern France, Macron said that it was important to give Ukraine "the means to last, and to enter any future negotiations from a position of strength".

"The challenge tomorrow, when hostilities cease, will be to give Ukraine guarantees against any return to war on its territory, and assurances for our own security."

Macron has repeatedly called on Europe to assume more responsibility for its own defence, and he reiterated that call on Monday.

"There can be no peace and security in Europe without Europeans," Macron said, referring to the Ukraine war and to European involvement in the negotiations.

Trump has questioned Washington's commitment to defend NATO allies and spoken of slashing support to Ukraine.

His return to the White House is a renewed spur to Europeans, long used to conventional and nuclear protection from the US military, to reexamine their own defence.

"What will we do in Europe tomorrow if our American ally withdraws its warships from the Mediterranean? If they send their fighter planes from the Atlantic to the Pacific?" Macron said.

"The answer will have to come from us."

In 2023, France adopted a 413-billion-euro ($450 billion) military budget for 2024-2030, its most significant spending increase in decades.

- Mobilising young volunteers -

Macron also asked the government and the armed forces to submit proposals by May on how to mobilise more young volunteers to "back up the armed forces" in case of need, seeming to acknowledge the end of the universal national service project that he had long championed.

"In order to build up this reserve, the Defence and Citizenship Day will be revamped," he added without providing more details about the proposal.

France requires all citizens to participate in a one-day "Defence and Citizenship" course when they turn 18, which includes a presentation of the country's military forces and a French language test.

"We will have to do a better job of identifying volunteers," Macron said.

France's last conscripts were demobilised in 2001.

During his presidential campaign in 2017, Macron promised to introduce a month-long compulsory national service, saying he wanted to give young French people "a direct experience of military life".

The proposal received a cool response from the army, prompting the government to come back with proposals for a compulsory civic service instead.

In 2019, France began a trial project and French authorities planned to eventually make the "Universal National Service" (SNU) compulsory but the country's political crisis has put the brakes on the development of such a plan.

France wants to have 210,000 active servicemen and 80,000 reservists by 2030.

More broadly, Macron said he was launching an update of France's military strategy, tasking officials with submitting proposals on how to adapt to modern "perils" between now and May.