HOHHOT, Sept. 11 (Xinhua) -- Chinese President Xi Jinping on Monday stressed global cooperation to combat desertification, which he said is a common challenge for mankind.

Xi made the remarks in a congratulatory letter to a high-level meeting of the 13th session of the Conference of the Parties (COP13) to the United Nations Convention to Combat Desertification (UNCCD), which opened Monday in Ordos City in north China's Inner Mongolia Autonomous Region.