China strongly warned a high-level Japanese official around late June that Tokyo should not send Self-Defense Forces to join U.S. operations that test the freedom of navigation in the disputed South China Sea, diplomatic sources said Saturday.
Japan will "cross a red line" if SDF vessels take part in so-called freedom of navigation operations, Ambassador Cheng Yonghua told the official, the sources said. Cheng even hinted at military action.
The warning was issued not long before an international tribunal ruled on conflicting claims in those waters.