Marcin Bosacki added that the bloc "simply must find the resources" to support Kyiv.
He spoke in Brussels, where he attended a meeting of EU foreign ministers.
"Without new funds, it’s hard to imagine Ukraine continuing its effective fight against Russia," Bosacki said.
Earlier this month, the European Commission proposed two financing options: a loan secured against frozen Russian assets or a loan taken out directly by the EU.
The first option would not require unanimous approval by member states, while the second would, officials have said.
European Commission chief Ursula von der Leyen said either plan would cover about two-thirds of Ukraine’s financial needs for 2026 and 2027, Polish state news agency PAP reported.
EU foreign ministers were scheduled to hold a video conference with US special envoy Steve Witkoff and Jared Kushner, President Donald Trump's son-in-law, later on Monday.
Bosacki said the talks underscored Washington's willingness to engage directly with European partners.
"The United States is and will remain the broker of peace talks," Bosacki said. "Only Donald Trump and his team are able to mediate between Ukrainians and Russians."
The ongoing negotiations are focused on three main issues, according to Bosacki.
The first is territory, he said, adding that Poland opposes any peace plan that would require Ukraine to cede sovereign land to Russia.
"Here we support Ukraine unequivocally," Bosacki told the media.
The second issue is financing, with the EU expected to decide later this week.
Bosacki said Poland supports a loan secured against Russian assets, though views among EU members differ.
The third issue involves security guarantees for Ukraine, with positions among Kyiv, Washington and European capitals "moving closer together," he said.
Asked about Ukrainian President Volodymyr Zelensky’s planned visit to Poland later this week, Bosacki called it "a positive development" and noted that it would mark Zelensky's first meeting with Polish President Karol Nawrocki since Nawrocki's election six months ago.
Bosacki added that Polish Prime Minister Donald Tusk remained in frequent contact with Zelensky and was likely to speak with him during the visit.
Poland supports Ukraine not only for moral reasons, Bosacki said, but also out of national interest.
"A Russian conquest of Ukraine would be a strategic nightmare for Poland," he told reporters.
(pm/gs)
Source: PAP