Chinese President Xi Jinping sent a message to the fifth China-U.S. Sister Cities Conference on Friday, saying the close cooperation between sister provinces/states and sister cities has been fruitful over the past four decades.

The foundation of China-U.S. relations lies in the people and the source of strength lies in the friendship between the people, Xi said in his message to the conference held in Suzhou in east China's Jiangsu Province.

Sister provinces/states and sister cities are important platforms for deepening friendship and achieving win-win cooperation, Xi said, noting that 284 pairs have been formed since the first pair was set in 1979.

Sister provinces/states and sister cities have engaged in close, productive cooperation over the past four decades, bringing tangible benefits to the two peoples, Xi said.

He stressed that the China-U.S. Sister Cities Conference is an important mechanism for sub-national exchanges and it has played a positive role in promoting the development and cooperation between sister cities.

He called on the participants of the conference to continue to serve as a bridge for sub-national exchanges, enabling the provinces/states and cities to play a greater role in promoting the sound and steady development of bilateral relations and improving the well-being of the two peoples.

The conference, themed "Build Green Cities for the People," is co-hosted by the Chinese People's Association for Friendship with Foreign Countries and the Jiangsu provincial government.