The Department of Homeland Security stated that using DeepSeek may result in the transfer of sensitive data belonging to U.S. government employees or vendors to the Chinese government.

From the articleUS civilian agencies can’t use DeepSeek, DHS says.Also in US banning Chinese AI DeepSeek from government agency IT systems | Reuters, US bans DeepSeek from government IT systems, Homeland Security bans DeepSeek use in federal civilian agencies - Engadget, US government bars DeepSeek from civilian agency use, US Orders Civilian Agencies to Rip DeepSeek Out of Government Systems - Decrypt