As a window for China's opening-up, the coastal city of Qingdao in Shandong province is participating in international economic and trade cooperation.

The city is also enhancing ties with multinational companies under the Regional Comprehensive Economic Partnership, according to local officials.

The RCEP is the world's largest free trade agreement. It plays a vital part in boosting the country's dual-circulation development paradigm that takes the domestic market as the mainstay while letting domestic and foreign markets complement each other.

Accounting for roughly 30 percent of the world's population, GDP and trade, RCEP countries create the world's largest free trade bloc by economic size, making it the biggest driver of global economic growth.

Lu Zhiyuan, deputy Party secretary of Shandong and Party secretary of Qingdao, said at the RCEP economic and trade cooperation meeting of the third Qingdao Multinationals Summit that the city will pay more attention to the main role of enterprises. It'll especially focus on multinational companies to facilitate trade, services, investment and safe and efficient supervision.

According to the Qingdao bureau of commerce, the city invites many multinational enterprises to join hands to explore new opportunities under the RCEP.

It also invites them to cooperate and share the dividends of international trade, while promoting the development of the service industry and expanding two-way investment and the domestic consumption market. "The RCEP not only provides a healthy environment for trade, but also for investment," said Tsunetaka Mori, vice-president of Itochu Corporation's East Asia operation.

He said he is looking forward to working with Qingdao to jointly explore the huge potential of China's hydrogen energy market and open up new markets including Japan.

On June 18, the launch ceremony of the China-Japan RCEP Maritime Express was held in Dagang Port in Qingdao.

The express set sail in Shibei district, connecting shipping, trade and finance.

It has become an important conduit for trade in northern China, and also served as the prelude to the joint construction of the China-Japan logistics center under the RCEP.

Li Wucheng, general manager of Qingdao Port Group, said that the express is the first line between northern China and Japan to foster trade among China, Japan and South Korea.

"The entire voyage takes 36 hours, which saves nearly half of the time compared to general cargo liner which requires two to three days of sailing time.

"It can achieve pre-clearance upon arrival. The import of 2,500 cars will save additional time and cost for cargo owners and effectively promote the development of cross-border trade," he said.

Wang Lijun, general manager of Sinotrans Central China, said under the line, the company will develop businesses such as assembly, import and export, while promoting the digital transformation of the industry and providing customers with more efficient end-to-end integrated logistics services.