EU chief Charles Michel on Thursday said that tanks "must be delivered" to Ukraine as he visited the war-torn country.
Michel travelled to Kyiv on the eve of a major meeting at the US military base of Ramstein in Germany to discuss military aid to Ukraine on Friday.
"I firmly believe that tanks must be delivered," Michel tweeted after talks with Ukrainian President Volodymyr Zelensky.
"We want to support you because we are aware that the next few weeks may be decisive for what comes next," he wrote.
"We hear your message. You need more air defence and artillery systems, more ammunitions."
Zelensky for his part called his talks with Michel "meaningful."
"Ukraine and the European Union have already achieved significant results in our historic rapprochement," he tweeted.
"We are working to achieve even more."
Zelensky has called for modern, Western-designed heavy tanks while many of Ukraine's allies have announced plans to step up their military support to Kyiv this month.
Michel earlier hailed the Ukrainians "fighting for their land, they are fighting for their future and the future of their children".
"But we all know that they are also fighting for our common European values and principles, and also for the promise of the European Union peace and prosperity," he said. "They need and they deserve our support."
Meanwhile, Ukrainian President Volodymyr Zelensky said late Thursday that he expected "strong decisions" on further Western arms supplies at a key meeting of allies at the US Ramstein airbase in Germany on Friday.
"As we prepare for tomorrow's Ramstein, we expect strong decisions. We expect a powerful military support package from the United States," he said.
Ahead of the talks, pressure has been growing on Berlin to approve the delivery of German-made Leopard 2 tanks, which are keenly sought after by officials in Kyiv to press offensives against Russian troops.
Poland and Finland have indicated they would be willing to send the tanks to Ukraine, but need German approval for the move.
"I am grateful to Charles Michel, President of the European Council, who was in Kyiv today and who very clearly calls on Europe to make a decision on tanks," Zelensky said.
"Now we are waiting for a decision from one European capital that will activate the prepared chains of cooperation on tanks," he said, adding: "I believe that the strength of German leadership will remain unchanged."
