Chinese President Xi Jinping offered his congratulations in a letter to the 2019 China Marine Economy Expo that opened Tuesday in the city of Shenzhen, south China's Guangdong province.

Xi, also general secretary of the Communist Party of China Central Committee and chairman of the Central Military Commission, expressed his warm welcome to guests from all over the world in the letter.

"The oceans play a significant role in the existence and development of human society. They provide a breeding ground for life, connect the world and promote development," Xi said in the letter.

Xi called for efforts to accelerate marine sci-tech innovation, improve marine development capacity, and foster and strengthen emerging marine industries of strategic importance.

He urged efforts to promote marine connectivity and cooperation in all areas, and develop a "blue partnership" among all countries.

Xi stressed marine ecological conservation, marine pollution prevention and treatment, protection of marine biodiversity, orderly development and utilization of marine resources, in a bid to leave a clean and tidy marine environment to future generations.