A new study says China's economy will surpass the United States by 2035, and double by mid-century.

The study released Tuesday by a Washington-based research institute predicts that China's economic growth is driven by domestic demand, and not exports.

For that reason, the report's author Albert Keidel says strong growth will continue into the 21st century regardless of a downturn in the world market.

China's economy has grown at an average annual rate of more than 10 percent over the last decade.  The country's Gross Domestic Product currently ranks fourth behind the United States, Japan and Germany based on 2007 figures.

Keidel is an expert on China's economy at the Carnegie Endowment for International Peace.  He formerly held positions at the U.S. Treasury Department and the World Bank.

Some information for this report provided by AFP.