GUANGZHOU: Construction of a cross-sea bridge - the world's second longest - linking the island of Hainan with the mainland is likely to begin in 2012, local media said yesterday.

The 30-km cross-sea expressway, the longest in the world after China's 36-km Hangzhou Bay Bridge, is expected to reduce the traveling time between Guangdong and Hainan to 20 minutes once it is opened to traffic in 2020.

After 14 years of research and negotiations, the ministries of communications and railway and the provincial governments of Guangdong and Hainan signed an agreement in Beijing to jointly submit a project proposal to the State Development and Reform Commission, the Guangzhou-based Southern Metropolis Daily reported.

The bridge, which will traverse 26.3 km of sea, will be jointly constructed by the four parties at a cost of more than 20 billion yuan ($2.92 billion).

Hainan, the country's second largest island, will be connected with the mainland by advanced highway and railway networks after the double-decker bridge, spanning the Qiongzhou Strait, becomes operational.

Currently, it takes a 5-hour ferry ride to get to Hainan from the mainland.

The structure is designed to reach a speed of 100 kph for vehicles and 160 kph for trains, cutting the travel time between the two provinces by more than 4 hours, the newspaper said.

The ministries of communication and railway, and the governments of Hainan and Guangdong have established a special task force to handle the first-phase of the project.

An official from Guangdong provincial development and reform commission said the bridge would help expand economic ties between Guangdong and Hainan provinces as well as the neighboring Guangxi Zhuang autonomous region.

Guangdong, which lacks natural resources and energies to support its economic construction, is expecting to expand economic cooperation with Hainan, known for its rich reserves of offshore natural gas and crude oils, the official, who did not want to be named, said.

Guangdong's Leizhou Peninsula and cities in the southwestern part of the province will benefit from the project, he added.

The bridge will also help further expand economic ties with the Pan Pearl River Delta region, boost the economic growth of the Beibu Bay areas and speed up the construction of the China-ASEAN free trade zone, the official said.