Some diplomats in China have voiced concerns over President Xi Jinping's possible indefinite rule, warning that Beijing is set to adopt a tougher approach toward smaller Asian countries to expand its clout in the region.

Most members of the Association of Southeast Asian Nations have maintained amicable ties with Japan, Asia's second-largest economy after China, but they may start to keep their distance from Tokyo to protect their national interests over the next two decades, the diplomats said.

On Tuesday, the annual session of China's rubber-stamp parliament closed, after laying the groundwork for achieving Xi's goal of turning China into a "great modern socialist country" by the middle of the 21st century.