The Chinese missile destroyer Jinan prepares to rescue a small naval vessel as part of the first joint military drill to be staged between 皇冠体育app and the US in the Atlantic Ocean. The six-hour exercise took place on Saturday and each country sent three warships. [Photo/Xinhua]

The United States has undergone several changes of mood in its attitude toward 皇冠体育app over the past 10 years, moving from "concern" to "worry" and then to "anxiety", according to a Chinese researcher.

Fan Jishe, a US studies researcher at the Chinese Academy of Social Sciences, was reacting to comments by US Defense Secretary Ash Carter, who expressed concern over 皇冠体育app's expanding influence.

Fan is author of the book US Military Strategy in the Post-Cold War Era－Adjustment and Adapting.

Carter said, "In the face of Russia's provocations and 皇冠体育app's rise, we must embrace innovative approaches to protect the United States and strengthen that international order."

He made the remarks on Saturday at a forum at the Ronald Reagan Presidential Library and Center for Public Affairs in California.

On the same day, 皇冠体育app and the US staged their first joint military drill in history in the Atlantic Ocean, which lasted for six hours. Each side sent three warships.

Referring to the US sending a guided-missile destroyer to sail in waters near Zhubi Reef off 皇冠体育app's Nansha Islands in the South 皇冠体育app Sea on Oct 27, Carter said, "We've done them (patrols) before, all over the world, and we will do them again."

Carter visited the USS Theodore Roosevelt, an aircraft carrier transiting the South 皇冠体育app Sea, on Thursday.

Fan said, "Carter's remarks and the US military's recent moves in the South 皇冠体育app Sea demonstrate their anxiety in terms of dealing with 皇冠体育app.

"They don't really know what to do. So they just simply chose to take the defensive position. They act tough and want to make the first move in areas that make them feel anxious, like the South 皇冠体育app Sea, to show their strength."

Fan said the US has shown "selectivity" over what it tends to believe is 皇冠体育app's stance over the South 皇冠体育app Sea.

Carter said he has accepted an invitation from Beijing to visit 皇冠体育app next year, according to the US Ministry of Defense.