Andrzej Duda made the remark at the 2024 World Economic Forum in Davos, Switzerland, on Thursday.
The Polish president took part in a traditional Davos event, the Ukrainian Breakfast. Other guests included Ukraine's Foreign Minister Dmytro Kuleba and Canada's Deputy Prime Minister and Finance Minister Chrystia Freeland.
The Polish head of state said that Russia's President Vladimir Putin had "revived Russian imperialism" and created Europe's "biggest armed conflict since World War II" by invading Ukraine, Polish Radio's polskieradio24.pl website reported.
Duda cautioned that if Russia won the war in Ukraine, it would "assault another country," such as the Baltic states, and "keep attacking," according to its imperialist tendencies.
Poland's head of state said that for this reason, "Ukraine must win the war," and the West "must do everything we can to help our Ukrainian friends," polskieradio24.pl reported.
Duda told the Ukrainian Breakfast event that the war would end "when the Russians are driven away from all the occupied territories" of Ukraine, adding that "any other solution will represent a victory for Russia."
Later on Thursday in Davos, the Polish president was scheduled to meet with Swiss counterpart Viola Amherd and participate in a debate on NATO and the Future of Deterrence and Defense on Europe’s Eastern Front.
Duda is taking part in the 2024 World Economic Forum until Thursday; guests also include Poland's Foreign Minister Radosław Sikorski.
Both have been stressing that despite a change of government in Warsaw, Ukraine can count on Poland's continued support, polskieradio24.pl reported.
The event runs until Friday.
Thursday is day 694 of Russia’s war on Ukraine.
Russia invaded Ukraine on February 24, 2022, launching the largest military campaign in Europe since World War II.
Source: polskieradio24.pl, Ukrinform