The highest-level U.S. delegation to Cuba in decades kicked off two days of negotiations Wednesday after grand promises by President Barack Obama about change on the island and a somber warning from Cuba to abandon hopes of reforming the communist government.

U.S. moves to restore diplomatic relations with Cuba and loosen the five-decade trade embargo have “the potential to end a legacy of mistrust in our hemisphere” and have “added up to new hope for the future in Cuba,” Obama said in his State of the Union address Tuesday night.