China will face great difficulty in achieving economic growth above 6.5 percent over the 2016-2020 period due to slowing global demand and rising labor costs at home, the China Securities Journal quotes a top state adviser as saying.

Li Wei, president of the State Council's Development Research Centre, made the comments at a conference over the weekend, the newspaper reported on Monday.

"In the last 30 years of reforms and opening up, China's gross domestic product has posted annual growth of around 10 percent. Against this, 6.5 percent is not high, but it will be very difficult to achieve this pace of growth," he said.

He said the main impeding factors were a likely global economic slowdown, rising labor costs that were eroding China's competitive advantage, and growing environmental concerns which meant that the country could not industrialize arable land at as rapid a pace as before.

President Xi Jinping has said that China must keep annual average growth at no less than 6.5 percent over the next five years to hit the country's goal of doubling gross domestic product and per capita income by 2020 from 2010.

China is set to release fourth-quarter and full-year GDP data on Jan. 19. It is expected to report 2015 growth cooled to around 7 percent, the slowest in a quarter of a century.