North Korea insisted that the U.S. could send its president, vice president and all 535 members of Congress to see if they are creating biological weapons such as anthrax, the Yonhap News Agency reported Monday.

The spokesperson for the policy bureau of North Korea’s supreme political body, the National Defense Commission, issued a statement strongly denying that the country’s Pyongyang Biotechnical Institute is being used to manufacture anthrax, and suggested that the U.S. come to visit.