China has made remarkable achievements in the past decade thanks to its huge trade surplus and now it turns to gain momentum from domestic demand, Jim O'Neill, chief economist at Goldman Sachs, said Monday.

O'Neil, who first dubbed China, India, Russia and Brazil "Bric" in 2001, told Xinhua that China could be "the largest economy in the world" in 2027 with its GDP of $21 trillion, and its consumption could be $10 trillion, or nearly 50 percent of the whole GDP.

He said Goldman Sachs expects China's GDP to increase by 9.4 percent and its domestic demand up 13.3 percent this year, and in 2010 both figures could be even bigger.

However, the average growth rate of China's GDP between 2011 and 2020 is estimated at 7.7 percent, and gradually scales down in the next few decades, O'Neil said citing a Goldman Sachs report during a news conference.

When asked about serious challenges that could hinder China's economic growth, O'Neill said domestic demand was so important that China should continue to put in more effort. He said a sophisticated social security system was another priority.

Helen Qiao, a China economist with Goldman Sachs, said it could take a long time for China's economic structure to redress the balance.

"China's savings rate could decline 5 percentage points by 2015, and another 12 percentage points from 2015 to 2025. It represents a good sign for the increase of consumption," Qiao mentioned in her report: Outlook on Global and China's Macroeconomy.

Statistics showed that in 2008 China's GDP ranked third after the United States and Japan. And China's contribution to global economic growth amounted to 22 percent, surpassing the United States to be the world's No. 1. The figure was expected to be 50 percent this year.