SHENZHEN, June 30 -- Chinese President Xi Jinping on Sunday sent a congratulatory letter as a cross-sea passage opened, linking the cities of Shenzhen and Zhongshan in southern China's Guangdong Province.

Xi, also general secretary of the Communist Party of China Central Committee and chairman of the Central Military Commission, said the Shenzhen-Zhongshan Link is another large-scale transportation project in the Guangdong-Hong Kong-Macao Greater Bay Area following the Hong Kong-Zhuhai-Macao Bridge. The project managed to overcome multiple world-class technical challenges and set multiple world records.

All participants, through their hard work and unwavering determination, have successfully completed the project with high quality, Xi said.

"This fully illustrates that Chinese modernization can only be achieved through solid work, as all great causes are accomplished through concrete actions," he said.

Xi underscored efforts to manage and make good use of the passage, and promote infrastructure connectivity and alignment of rules and mechanisms to facilitate the building of an integrated market in the Greater Bay Area.

Spanning 24 km, the passage cuts travel time between the city of Zhongshan and the technology hub of Shenzhen -- situated on opposite sides of the Pearl River Estuary in Guangdong Province -- from two hours to approximately 30 minutes.

The construction of the project began in February 2017. The new link marks the world's first cross-sea cluster project that features two bridges, two artificial islands, and an underwater tunnel.