America's third largest city, Chicago, signed a five-year plan Wednesday with eight Chinese cities to promote cooperation in advanced manufacturing and innovative technologies.

The deal, named 2018-2023 Key Sectors Joint Work Plan, was signed at a forum held in Beijing and hailed as a milestone by Chicago Mayor Rahm Emanuel who led a delegation to visit China for closer business ties.

"An open, confident, cooperative and competitive relationship is something we seek," Emanuel said at the 2018 China-Chicago Gateway Cities Investment Cooperation Forum.

Trade between Chicago and China has grown 100 percent since signing the cooperation deal five years ago between the city and major Chinese cities including Beijing and Shanghai, the mayor said.

"Chicago started something and embarked on a different road five years ago," he said. "If we do this right..., the rain will disappear, the sun will come out, and something beautiful will grow."

Li Chenggang, China's assistant commerce minister, said at the forum that the Chicago delegation's visit displayed support for free trade and opposition to protectionism.

"Under the current situation, the visit showed U.S. local governments and industries are confident in the future of China-U.S. economic and trade cooperation."