NANNING, Sept.4 (Xinhua) -- Investors in China's western interior will no longer have to make detours to eastern and southern coasts for imports or exports as a railways network will allow them easier access to local sea port in Beibu Bay in six years, says the local railway authority.

    The ongoing railway expansion consists of four regional trunk lines: Lanzhou-Urumqi, Lanzhou-Chongqing, Guiyang-Chongqing and Huangtong-Baise railways. The network passes through 12 provinces from north to south in the western region, Nanning Railway Bureau director Chen Baoshi said on Friday.

    On completion of the network in 2015, the only passage to the sea in the western region would be operational, he said. He did not give details of construction costs.

    Zhang Jiashou, director of economic department of Party School in Guangxi Zhuang Autonomous Region, said Beibu Bay had become a stronger and busier sea transportation hub as a result of deepened collaboration between China and the Association of Southeast Asian Nations (ASEAN).

    But inadequate road and rail networks in the west made it difficult for business in the northwest to get to the port on the southern border which was the closest geographically, he said.

    Zhang said he expected the new network to energize local business activities and optimize the investment environment by facilitating the region's collaboration with ASEAN and the Pearl River Delta.

    The interior West has an aggregate population of 28 million and its 5.4 million sq km accounts for 56.2 percent of China's land mass.