Poland will not hand over its MiG-29 fighter jets to Ukraine after Kyiv declined to share drone-production technology with Warsaw, Poland’s defense minister Władysław Kosiniak-Kamysz said.

Kosiniak-Kamysz said Warsaw had proposed a “partner-based approach” under which Ukraine would provide access to Ukrainian drone know-how and technological expertise in exchange for the MiG-29s. He said Ukraine initially agreed but then did not follow through on the arrangement.

“There will be no MiGs for Ukraine because there are no drones—or rather, no drone capabilities—for Poland,” Kosiniak-Kamysz said, arguing the swap depended on Ukraine delivering the agreed unmanned-systems capabilities.

The minister added that Ukraine has significant expertise in unmanned systems and had the ability to share part of that technological knowledge in return for Poland’s military assistance, but that it stepped back from the deal.

Ukrainian officials have not publicly commented on the Polish defense minister’s claims.