EU chief Ursula von der Leyen (L) and US President Donald Trump
Von der Leyen's demand comes as the Kremlin continues to stall on Trump's push to set up direct talks between Putin and Zelenskyy to end Russia's invasion of Ukraine.
"Just spoke with President Zelenskyy, then President Trump, following the massive strike on Kyiv which also hit our EU offices. Putin must come to the negotiating table," European Commission head von der Leyen wrote on X.
"We must secure a just and lasting peace for Ukraine with firm and credible security guarantees that will turn the country into a steel porcupine," she added.
Moscow meanwhile launched one of its biggest overnight bombardments of the conflict in Ukraine, killing at least 17 people in Kyiv and damaging the European Union's diplomatic mission.
As part of the US-led peace efforts, Western powers are currently also discussing how to guarantee Ukraine's security if any truce deal comes into force.
Trump has indicated the United States could play a role backing up any European peacekeeping plan, but would not deploy American soldiers to Ukraine.
Von der Leyen wrote that "Europe will fully play its part", highlighting a major new EU programme designed to help fund arms for Ukraine.
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