The “coalition of the willing” is ready to protect peace, should it arrive, in Ukraine.

That’s the message President Emmanuel Macron of France wants to deliver with more than 30 other heads of state and government, including President Volodymyr Zelensky of Ukraine, on Thursday, when they are expected to join, many of them virtually, a meeting in Paris.

After weeks of technical meetings between military representatives of the countries known as the coalition of the willing, the political leaders will review detailed options to secure any cease-fire or peace deal, and present enough contributions to show a serious, initial commitment to the plans, according to three highly placed French diplomats who spoke anonymously to discuss high-level matters.

“Europe is stepping up for the first time with this level of commitment and intensity, because the security of Ukraine and of Ukrainians, today and tomorrow, is also ours and Europe’s,” Mr. Macron, with Mr. Zelensky at his side, told the press on Wednesday night.

While the message might comfort Mr. Zelensky, it is aimed at President Trump, who has made clear his ambitions to end the three-year war in Ukraine, but delivered conflicting statements on who is to blame for the Russian invasion and how it might be settled.

“Europeans want to show that they’re doing their homework, that they are able to provide real security capabilities to Ukraine, something that would make a difference after a potential cease-fire,” said Martin Quencez, the director of the Paris office of the German Marshall Fund. “But perhaps more importantly, it is a message to the United States.”

The questions will be whether the plan is detailed enough, the commitments are firm enough and the coalition is united enough to persuade Mr. Trump not only to increase his support for Ukraine in the event of an end to the war, but also to put real pressure on President Vladimir V. Putin of Russia to end the invasion.