The leaders of Britain, France, Germany and Poland plan to make their first-ever joint visit to Kyiv on Saturday, in an effort to underscore their support for Ukraine and reinforce calls for Russia to agree to a 30-day cease-fire.

During a trip intended to showcase European unity, France’s president, Emmanuel Macron, the new German chancellor, Friedrich Merz, and the British and Polish prime ministers, Keir Starmer and Donald Tusk, are expected to hold talks with the Ukrainian president, Volodymyr Zelensky.

The visit to Ukraine will be the first for Mr. Merz as German chancellor, and is the first time leaders of four European nations have traveled together to Ukrainian soil.

It also comes one day after President Vladimir V. Putin of Russia welcomed the presidents of China and Brazil, among other international officials, to Moscow to mark the 80th anniversary of the defeat of Nazi Germany with a military parade, intended to place Russia at the vanguard of a rising, non-Western world order.

Ahead of the visit, the four European nations voiced support for President Trump’s call, first made in March, for a 30-day cease-fire in the conflict between Ukraine and Russia. Ukraine agreed to Mr. Trump’s proposal, but Russia has pushed instead for negotiating the terms of a settlement before any sustained pause in hostilities.

“We reiterate our backing for President Trump’s calls for a peace deal and call on Russia to stop obstructing efforts to secure an enduring peace,” the four countries said in a joint statement issued late Friday. “Alongside the U.S., we call on Russia to agree a full and unconditional 30-day cease-fire to create the space for talks on a just and lasting peace.”