French President Emmanuel Macron said he's not "ruling out" sending troops into Ukraine if Russian forces break through the front lines or if officials in Kyiv request assistance, saying the security of Europe is at stake.

"If the Russians were to break through the front lines, if there were a Ukrainian request, which is not the case today, we would legitimately have to ask ourselves this question," the French leader said in an interview published Thursday in the Economist.

Macron was asked in the interview about comments he made earlier this year about the possibility of Western troops being deployed in Ukraine.

"Absolutely. As I said, I'm not ruling anything out, because we are facing someone who is not ruling anything out," he said.

Macron said Russian President Vladimir Putin's aggression has destabilized the region and his mounting threats pose an existential threat to Europe.

"I have a clear strategic objective: Russia cannot win in Ukraine," Macron said.

"If Russia wins in Ukraine, there will be no security in Europe," he told the outlet. "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?"