The question of sending western troops to Ukraine would "legitimately" arise if Russia broke through Ukrainian front lines and Kyiv asked, French President Emmanuel Macron has said.
Mr Macron's comments to The Economist, published on Thursday, repeat those he made this year where he said he would not rule out sending troops to Ukraine.
It sent shockwaves through Europe and unsettled allies including Germany. Most of France's allies said at the time they would not send any troops.
He gave the interview after delivering a speech last week in which he declared that Europe is "mortal" and could "die" partly due to the threat posed by Russian aggression after its February 2022 invasion of Ukraine.
It was published at a key moment for Mr Macron, who is due to host Chinese President Xi Jinping on May 6 and 7 for a state visit, and has been issuing increasingly stark warnings about the threat posed by Russia.
"Absolutely. I'm not ruling anything out, because we are facing someone who is not ruling anything out," he said when asked if he stood by his earlier comments from February 26.
Mr Macron said that "if Russia decided to go further, we will in any case all have to ask ourselves this question" about sending troops, describing his refusal to rule out such a move as a "strategic wake-up call for my counterparts".
His latest comments come as some analysts believe that Russia could be on the verge of launching a major new offensive in Ukraine.
Weapons wanted by Ukraine - in pictures
Russia said on Thursday that it had captured another village in eastern Ukraine, where its forces have been making advances for days.
In an apparent bid to keep harmony with Berlin before Mr Xi's visit, Mr Macron was due to dine privately on Thursday with German Chancellor Olaf Scholz at a Paris restaurant, a French presidential official said.
Russia under Vladimir Putin as 'a power of regional destabilisation'
Mr Macron described Russia under President Vladimir Putin as "a power of regional destabilisation" and "a threat to Europeans' security".
"I have a clear strategic objective: Russia cannot win in Ukraine," Mr Macron said.
"If Russia wins in Ukraine, there will be no security in Europe. Who can pretend that Russia will stop there?
"What security will there be for the other neighbouring countries, Moldova, Romania, Poland, Lithuania and the others?
"It has broken all the frameworks and has basically returned to a logic of total war."
But he suggested that Moscow's war machine was not sustainable over the long term.
"Devoting a third of its budget to defence is not sustainable for a country whose gross domestic product is lower than that of France, Germany or the United Kingdom," he said.
'Europe must reduce its defence dependence on the US'
Restating that Europe must reduce its defence dependence on the US, Mr Macron said the EU needed a "credible strategic concept of joint defence" adding that "nuclear weapons must be included in the debate".
After Britain's exit from the EU, France is the bloc's only power with its own atomic weapons.
Hungary, whose Prime Minister Viktor Orban is seen as the strongest supporter of Mr Putin in the EU, took issue with Mr Macron's latest statements.
"If a Nato member commits ground troops, it will be a direct Nato-Russia confrontation, and then it will be World War III," Hungarian Foreign Minister Peter Szijjarto said.
Ukraine's war with Russia is 'the challenge of our generation'
British Foreign Secretary David Cameron visited Ukraine on Thursday and met President, Volodymyr Zelenskyy, to whom he reaffirmed the UK's "unequivocal support".
In Kyiv, Lord Cameron announced that the UK's donation of military equipment would include precision-guided bombs, air defence missiles and equipment for 100 mobile air defence teams to enable Ukraine to shoot down Russia's drones and missiles.
He also confirmed a £36 million ($45.1 million) package of support, including £20 million in new emergency funding after Russia's recent attacks on Ukraine's infrastructure.
Lord Cameron said Ukraine's war with Russia is "the challenge of our generation".
"Ukraine is fiercely defending itself against Russia's illegal invasion, making a war Putin thought would last days, take years," he said.
"But this war is the challenge of our generation and Ukraine cannot fight it alone.
"We must all step up to ensure Ukraine has what it needs to win.
"Through our multi-year military funding, weapons provision and vital support to protect and repair Ukraine's energy infrastructure, the UK is standing with Ukraine and we will stand with Ukraine for as long as it takes."
Europe faces 'disruption to the functioning of our democracies'
Mr Macron also said in the interview that Europe faced not just a military and security risk, but also "an economic risk for our prosperity" and "an existential risk of internal incoherence and disruption to the functioning of our democracies".
"Things can fall apart very quickly," he said.
He said Europe must defend its "strategic interests" in its economic relations with China to address imbalances and restore "reciprocity" in economic ties.
Indicating that Ukraine would loom large in the talks with Mr Xi, Mr Macron said: "It's not in China's interest today to have a Russia that destabilises the international order."
With European Parliament elections next month in which the far-right is set to make gains in France, Mr Macron warned voters against voting for nationalists.
"I say to Europeans: Wake up … all European nationalists are hidden Brexiteers. It's all the same lies," he said.
"Make no mistake. If you entrust the keys to people who think like they do, there is no reason why Europe should become a great power."
