The Democrat made the comments at a meeting with reporters following her address to a joint session of the Nevada Legislature on Wednesday.
U.S. Department of Energy revealed earlier this year that it secretly shipped weapons-grade plutonium from South Carolina to a nuclear security site in Nevada. Cortez Masto has said she will oppose the agency's nominations until Perry agrees to set a date for removing the plutonium.
She says Perry called her recently about his concern with her holding up the nominees. The Democrat says she wants a written commitment from Perry before removing her nominee objections.