In a BBC interview to mark a year since Russia's full-scale invasion, he warned conceding land would mean Russia could "keep coming back", while Western weapons would bring peace closer.
Mr Zelensky also said a predicted spring offensive had already begun.
"Russian attacks are already happening from several directions," he said.
He does, however, believe Ukraine's forces can keep resisting Russia's advance until they are able to launch a counter-offensive - although he repeated his calls for more military aid from the West.