Japan's aggressive role in dealing with China was a continual source of tension—indeed eventually led to World War II between them. In 1917 the Lansing–Ishii Agreement was negotiated. Secretary of State Robert Lansing specified American acceptance that Manchuria was under Japanese control. While still nominally under Chinese sovereignty. Japanese Foreign Minister Ishii Kikujiro noted Japanese agreement not to limit American commercial opportunities elsewhere in China. The agreement also stated that neither would take advantage of the war in Europe to seek additional rights and privileges in Asia.