Speaking to reporters on Saturday, Tusk said he had received a warm personal letter from former Ukrainian President Viktor Yushchenko, urging both countries to work through their shared history so that "the past does not rule the future."
Tusk said the effort was worth making, but stressed that Ukraine needed to move first.
"It would be good to hear a very clear signal from Kyiv," he said.
"They are trying, but we would still like to hear it clearly.
What sparked the row
The dispute dates back to late May, when Zelensky named a special forces unit after the "Heroes of the UPA" (the Ukrainian Insurgent Army) – a World War II nationalist force – saying he wanted to honour the unit's role in defending Ukraine's territory and independence.
Many Ukrainians regard UPA members as national heroes for resisting both Nazi Germany and the Soviet Union and for their role in Ukraine's struggle for independence.
In Poland, however, the group is widely associated with the Volhynia massacres, a campaign of ethnic violence in 1943-1945 in which Polish authorities say about 100,000 Poles were killed by Ukrainian nationalists.
The move triggered strong criticism in Poland, including from Tusk and other senior ministers.
On 19 June, President Karol Nawrocki said he had decided to strip Zelensky of Poland's Order of the White Eagle.
The Ukrainian leader sent the medal back to Warsaw by courier the following day.
Poland's Foreign Minister Radosław Sikorski met his Ukrainian counterpart Andrii Sybiha in Warsaw on Friday to discuss relations between the two countries.
(ał)
Source: PAP