Former U.S. Deputy Secretary of State Richard Armitage said Wednesday in Tokyo that China is testing Japan over the "chill" in its ties with the U.S. by creating mischief in the East China Sea, particularly last week's collisions between a Chinese trawler and Japan Coast Guard vessels.

"My view is what China senses is a distracted United States who has a chilled relationship with Tokyo," Armitage said. "So they are testing what they can get away with."

During a speech at the Japan National Press Club in Tokyo, Armitage warned China that the U.S. military, based on the Japan-U.S. security treaty, would be obligated to take action if China begins engaging in more serious activities around the Senkaku islets.