Economic and policy experts are warning that Trump’s threatened border closure between the U.S. and Mexico could result in a hit of billions of dollars of losses to the economy by disrupting trade and the daily flow of goods and people between the two nations. Members of Trump’s own administration have expressed concerns with the possible closure; CNN reports one official warned the consequences could be “catastrophic.” It’s unclear whether Trump will follow through with his threat, which he announced Friday as a consequence if Mexico failed to stop several Central American caravans from arriving at the U.S. border. Last year, he also issued similar threats, once even saying he would close the border permanently.