The European Commission president suggested a group of "like-minded states" provide security guarantees to Ukraine.
A possible ceasefire in Ukraine would create a frozen conflict, increase regional instability and discourage the reconstruction of the war-torn country, as hostilities could "flare up again at any time," says Ursula von der Leyen.
"We want a just peace, one that does not reward the aggressor, but one that upholds the principles of the UN Charter, and the Ukrainian people's right to be masters of their own future," the European Commission president said in a speech delivered on Wednesday morning at the Globsec conference in Bratislava.
In her intervention, von der Leyen issued an unambiguous rejection of a ceasefire, which, in her view, would fail to end the large-scale invasion and simply consolidate the territorial gains made by Russia since February 2022.
The idea of a ceasefire has also been dismissed by Ukraine, which is preparing to launch a counter-offensive, but has received the endorsement of China and Brazil, two countries the West suspects of taking Moscow's side on the war.
"A ceasefire resulting in a frozen conflict will not bring lasting peace. After all, a ceasefire was in place after 2014 and we know what happened to that agreement last February when Russia invaded," von der Leyen said, referring to the Minsk agreements that were supposed to secure a truce in the Donbas region.
"A ceasefire would be inherently unstable and destabilize the region along the contact line. Nobody would invest or rebuild, and the conflict could flare up again at any time. No. A just peace must result in the withdrawal of the Russian forces and their equipment from the territory of Ukraine."
A just and lasting peace, von der Leyen continued, can only be realised through "long-term" security guarantees that would enhance Ukraine's defence capabilities and therefore dissuade the Kremlin from launching a new assault.
"A collection of such guarantees by like-minded states can offer what some have called 'deterrence by denial.' In other words, providing Ukraine with the military equipment to fortify itself against Russian attacks in the future," von der Leyen said.
This process, she added, should be done in parallel with Ukraine's democratic reforms, which are required to advance its EU accession bid.
The Commission chief did not specify which countries should form the group of "like-minded states" or whether the arrangement should be governed by NATO.
Ukrainian President Volodymyr Zelenskyy, who is pushing for his country to join the 31-strong alliance, has urged its members to provide "effective security guarantees" ahead of a NATO summit in July.
NATO Secretary General Jens Stoltenberg said earlier this month that "consultations" on this matter were ongoing but declined to give further details.
"The only way to ensure that that stops is partly to ensure that Ukraine has the military strength to deter and defend against further aggression from Russia but also to find some kind of framework to prevent President Putin from continuing to chip away at European security," Stoltenberg said.
Stoltenberg noted that if countries, "especially the big ones," were to offer security guarantees on a bilateral basis, this could risk the activation of Article 5, the alliance's collective defence mechanism.
"There's no way to find an easy solution to these issues," he said.