While receiving an interview from Japan's Kyodo News Agency, former U.S. Assistant Secretary of State Kurt Campbell said before Japan illegally purchased the Diaoyu Islands last year, the Obama administration raised objections because they thought Japan's move would trigger a regional dispute.

Former U.S. Assistant Secretary of State Kurt Campbell received an interview from Japan's Kyodo News Agency.

According to Campbell, the Japanese government asked for a U.S. opinion before it decided to "nationalize" the Diaoyu Islands. Japan believed that China would not object to the plan, but the U.S. thought Japan's outlook was overly optimistic.

The United States advised Japan to abandon its plans to "nationalize" the Diaoyu Islands, and the then Secretary of State Hillary Clinton had directly asked then Japanese Foreign Minister Koichiro Genba to "act with discretion."

Since Japan completed the "purchase" of the Diaoyu Islands in September 2012, tensions between China and Japan have escalated.

Campbell pointed out that it would be necessary for the Japanese side to reach an understanding with China before taking action. "Although the Japanese government thought it had gained supports from China, American didn't think so," he said.

Japan has admitted that?U.S. did request treating the Diaoyu Islands issue with caution.

China's Foreign Ministry reiterated that the Diaoyu Islands and adjacent islets have been an inalienable part of China's territory since ancient times. China has indisputable sovereign rights over them. Any unilateral action by Japan regarding the Diaoyu Islands is illegal and invalid.