During a call between U.S. President Donald Trump and his Ukrainian counterpart, the U.S. leader apparently suggested Volodymyr Zelenskyy consider transferring ownership of Ukraine’s power plants to the U.

The White House said taking ownership of Ukrainian plants would give them the “best protection.” The idea faces legal hurdles and operational challenges, and it’s unclear if Ukraine would agree to it.

Ukraine’s Zaporizhzhia nuclear plant must ‘remain Ukrainian,’ Zelesnky said Thursday. It’s occupied by Russia and would take years to restore.