UN Secretary-General Antonio Guterres said peace negotiations to end the conflict in Ukraine were "not possible at this moment," in an interview published by Spanish daily El Pais on Tuesday.
His statement came as the leaders of Russia and Ukraine both called for victory during events commemorating the end of World War II.
"It is clear that the [two] parties are completely absorbed in this war" and "are convinced that they can win," the UN chief was quoted as saying by the newspaper.
Guterres said he hoped it was possible "in the future" to bring Russia and Ukraine to the negotiating table.
Russian President Vladimir Putin said Tuesday at Moscow's Red Square Victory Day parade that the world was at a "turning point" and claimed a "war" had been unleashed against Russia.
The day before, Ukrainian President Volodymyr Zelensky vowed that Russian forces would be vanquished "just as Nazism was defeated."
On Tuesday, Guterres received the Carlos V European Award, given to individuals and organizations that have contributed to the enhancement of Europe's cultural and historical values or to EU integration.
"Universal values, principles and ideas which unite us as the human family... have not been under so much threat since the creation of the United Nations," Guterres said.
"That's why we have to raise our voice and reaffirm our values. And above all, we need peace," he added.
