South Korea's Unification Minister Chung Dong-young publicly identified a suspected North Korean nuclear site in Kusong, prompting the US to impose partial restrictions on intelligence sharing.
A senior military official told Yonhap news agency that Washington had imposed the restrictions since early this month, citing concerns over sensitive information being disclosed without authorisation.
The restrictions do not affect surveillance of missile activity or military readiness, according to reports. Chung has defended his remarks, saying they were based on publicly available research rather than classified intelligence.
South Korean President Lee Jae Myung backed his minister, stating that Kusong's existence had been widely reported in academic papers and media before Chung's remarks.
The restrictions come amid broader tensions in the alliance between South Korea and the US. The move has sparked controversy, with some calling for Chung's dismissal over concerns about national security.
North Korea is believed to have significantly expanded its nuclear programme in recent years, according to international experts.