Open Door policy, Statement of U.S. foreign policy toward China. Issued by U.S. secretary of state John Hay (1899), the statement reaffirmed the principle that all countries should have equal access to any Chinese port open to trade. The U.S. sent notes to Britain, Germany, France, Italy, Japan, and Russia explaining the policy to prevent them from establishing separate spheres of influence in China. Their replies were evasive, but the U.S. considered them acceptances of the policy. Japan’s violation of the policy in 1937 led the U.S. to impose an oil embargo. The policy was discontinued with the communist takeover of China in 1949.