The dispute centres on Polish President Karol Nawrocki's decision to strip Zelensky of the Order of the White Eagle, the country's highest honour.
Nawrocki ordered the medal's withdrawal on Friday after Ukraine named a military unit after the "Heroes of the UPA," referring to the nationalist force active during and after World War II.
The Ukrainian Insurgent Army (UPA) is seen very differently in the two countries. Poland holds it responsible for the 1943 massacres of Poles in the Volhynia and eastern Galicia regions of what was then German-occupied Poland, while Ukrainians largely view it as an anti-Soviet resistance movement.
Zelensky said at the weekend that he had sent the medal back to Warsaw.
On Monday, Polish presidential spokesman Rafał Leśkiewicz confirmed receiving it, though he said the withdrawal would only be formally completed once published with the prime minister's countersignature.
Zelensky said that before returning the decoration, Ukrainian officials had tried to defuse the conflict and explain Kyiv's position, and that he had proposed a meeting and joint press conference with Nawrocki.
'No real readiness to engage'
That account was disputed by Marcin Przydacz, head of the Polish president's International Policy Bureau, who said Ukraine had shown "no real readiness to engage" and had instead been stalling.
He added that a planned phone call between the two leaders fell through after Zelensky withdrew, and that Ukraine also pulled out of a planned visit to Warsaw, proposing a much later date instead.
In an interview with Ukrainian broadcaster TSN on Sunday, Zelensky suggested Nawrocki was using the dispute to strengthen his position in domestic politics against Prime Minister Donald Tusk, calling it an internal Polish matter.
Nawrocki rejected that argument on Monday, saying the dispute was about how the two countries view historical events, including Poland's refusal to accept nationalist symbols associated with the UPA.
Former Ukrainian presidents Leonid Kuchma, Viktor Yushchenko and Petro Poroshenko also announced on Saturday that they were giving up their Polish honours.
'Glorification of Ukrainian nationalists'
On Monday, Polish deputy upper-house Speaker Michał Kamiński said he was returning two awards he had received from Ukraine, linking his decision to what he called "Kyiv's glorification of Ukrainian nationalists responsible for the Volhynia massacre."
The row comes just before an international conference on Ukraine's reconstruction, due to be held in the Polish Baltic city of Gdańsk on Thursday and Friday, bringing together world leaders, government ministers and investors.
According to public broadcaster Polish Radio, citing unofficial sources, Zelensky will not attend, with Ukraine's delegation likely to be led instead by Prime Minister Yuliya Svyrydenko.
Nawrocki has not been invited.
Polish government spokesman Adam Szłapka cited the event's "format" as the reason the president was not invited, adding that the presidential palace had shown no interest in Nawrocki taking part.
(ał/gs)
Source: PAP, IAR