The Pentagon called Poland’s proposal to transfer jets into U.S. custody before sending them to Ukraine “high-risk” just a day after they labeled the deal not “tenable.”

Poland announced on Tuesday it would send its entire fleet of Russian-made MiG-29s to a U.S. military base in Germany before transferring them to Ukraine in response to pleas from Ukrainian President Volodymyr Zelensky. The Pentagon was unaware of the proposal before it went public, according to a senior defense official.