"This conflict will not end tomorrow or the day after," Macron said in his New Year's address to the French armed forces.

Macron spoke as the third anniversary of Russia's war against Ukraine approached next month and with Trump due to be sworn in as US president on Monday.

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, the French president 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 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'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.