Two men widely considered future leaders of China have made a rare appearance before the media, but both avoided questions on their political futures.

Shanghai Communist Party chief Xi Jinping and his counterpart in northeastern Liaoning province, Li Keqiang, spoke to reporters Tuesday after overseeing meetings of their delegations at the 17th Communist Party Congress in Beijing.

Both men were careful to refer to Chinese President Hu Jintao and his key themes at the Party Congress, including Mr. Hu's call for "scientific development" that balances economic growth with protecting the environment.

The 52-year-old Li and 54-year-old Xi are seen as possible contenders to replace President Hu and other leaders when they step down five years from now.

President Hu opened the Party Congress on Monday by saying political reform and economic growth in China must continue. He also emphasized that the Communist Party will remain in charge.

Mr. Hu pledged to allow more public participation in politics but offered few details. He warned that the Communist Party will not tolerate corruption.

China's Communist Party has been rocked in recent years by high-level corruption cases, including the arrest of a party boss in Shanghai.

The seven-day Party Congress is taking place at a time of increasing social unrest in China. Security is tight in Beijing, with reports of dissidents and other activists being detained to prevent unrest during the meeting.

The Party Congress is a crucial moment for Mr. Hu, as he sets Chinese policy for the next five years.

Party delegates are expected to re-elect Mr. Hu to another five-year term. They also will choose nine new members for the party's executive organization, the Political Bureau Standing Committee.

Some information for this report was provided by AFP, AP and Reuters.