BEIJING - A decade after China started its Western Development Program, the gap between its target regions and the eastern areas remains vast, a senior official said.

Du Ying, vice-minister of the National Development and Reform Commission (NDRC), likened the regions' development to "the shortest board" of the barrel at a news conference on Thursday.

The comparison referred to a well-known saying that the amount of water a barrel can contain is determined by the shortest, rather than the longest, stave of the cask.

"The entire country will not develop well if the western regions do not develop well," Du said, adding that the area is integral to national stability.

The area includes 12 provinces, regions and municipalities. It accounts for 71.5 percent of the country's territory and 27.5 percent of the mainland population.

The western regions are also home to 75 percent of ethnic minority groups and two-thirds of the country's population that lives below the national poverty line, delineated by an annual income of less than 1,196 yuan ($176).

The central government realized the region's importance and started the Western Development Program a decade ago, adopting preferential policies and supporting the regions' development. In the past decade, investment from the central and local governments, as well as from the private sector, has totaled nearly 20 trillion yuan, 5.5 times the amount invested from 1949 to 1999, the NDRC said.

Consequently, the regions maintained an 11.9-percent growth rate during the period and the impoverished population decreased by 70 percent to 23 million.

The central government plans to invest heavily in western China's economic development over the next 10 years. It aims to sustain double-digit annual growth from now until 2015, Du said.

A document released on Tuesday said the central government will this year invest more than $100 billion in 23 new infrastructure projects in the regions to boost domestic demand.

The NDRC is also imposing a trial 5 percent tax on resources exploited in the oil-rich Xinjiang Uygur autonomous region. If successful, the tax will be expanded nationwide, Du said.

Western China has abundant resources, including two-thirds of the country's extractable coal and natural gas reserves.

"The reform will certainly increase the resource-rich western region's fiscal income," Du said, without giving a timetable for the tax's expansion.