Volodymyr Zelenskyy started another intense diplomatic week on Monday after Ukraine concluded talks with US negotiators without a breakthrough, triggering criticism from Trump.
German Chancellor Friedrich Merz said on Monday that he was "sceptical" over certain aspects of the US-backed peace plan for Ukraine, following a meeting in London with Volodymyr Zelenskyy, Keir Starmer, and Emmanuel Macron.
The gathering in London followed the conclusion over the weekend of the latest round of talks between Ukrainian and US negotiators on a plan to end Russia's war in Ukraine.
"I'm sceptical about some of the details which we are seeing in the documents coming from the US side but we have to talk about that, that is why we are here," Merz said after the talks.
"This could be a decisive time for all of us so we are trying to continue our support for Ukraine," he added. "Nobody should doubt our support for Ukraine."
Speaking alongside him, France's President Macron said that Europeans "have a lot of cards in our hands" including the financing of delivery of equipment to Kyiv as well as "the fact that Ukraine is resisting in this war, the fact the Russian economy is starting to suffer".
"Now I think the main issue is the convergence between our common positions, Europeans and Ukrainians and the US, to finalise these peace negotiations and re-engage in new faith in the best possible conditions for Ukraine, for the Europeans and for our collective security," Macron stated.
Zelenskyy, whose meeting in London was the first stop in an intense diplomatic week to secure further support packages and air defence, said "unity" between Europe, Ukraine and Washington is "very important".
"There are some things which we can't manage without Americans, things which we can't manage without Europe," he said.
No breakthrough yet
Europeans, who are expected to shoulder the bulk of security guarantees if a ceasefire is struck between the two warring countries, have been scrambling to ensure their position is heard since a new peace plan draft hammered by Washington and Moscow that heavily favoured Russia was leaked in late November.
Subsequent talks in Moscow between Russian and US officials and in Miami between US and Ukrainian representatives have failed to provide a breakthrough.
One of the contentious points is that it envisions Ukraine ceding control of the entire Donbas region.
UK Prime Minister Starmer, who co-chairs with Macron the "Coalition of the Willing" — a group of European nations that stand ready to provide security guarantees for Ukraine — also pledged continued assistance.
"We stand here to support you in the conflict and support you in the negotiations to make sure this is a just and lasting settlement if we can get that," he said on Monday.
The show of support comes after US President Donald Trump criticised Zelenskyy, telling reporters on Sunday that the Ukrainian president "hasn't read the proposal" and "isn't ready" to sign off on it.
The Ukrainian president was expected in Brussels on Monday evening for talks with NATO Secretary-General Mark Rutte, and EU chiefs Ursula von der Leyen and António Costa, followed by a trip to Rome Tuesday for a meeting with Prime Minister Giorgia Meloni.