Global Internet retail sales topped $1 trillion for the first time in 2012 with the United States holding the top spot but China rising fast, a market research firm said Tuesday.

The report by eMarketer said ecommerce consumer sales grew 21.1 percent to just over $1 trillion, and are expected to grow another 18.3 percent in 2013, fueled by strong growth in Asia.

The research firm said North America remained the top region for ecommerce in 2012 with $364 billion in sales, up 13.9 percent.

But for 2013, the Asia-Pacific region is likely to be number one with 30 percent growth, which would bring the market to $433 billion, eMarketer said.

US ecommerce sales for 2012 were estimated at $343 billion, with Japan in second place at $127 billion, followed by Britain ($124 billion) and China ($110 billion).

But China was projected to vault into second place with 65 percent growth in 2013 to $181 billion. The US will remain the top market but growth will slow to 12 percent, for a total of $384 billion.

"Average spending per user is lower in China -- set to reach just $670 this year," eMarketer said in a statement. "But the sheer growth in China's digital buyers is staggering. The country will nearly double the number of people who buy goods online between 2012 and 2016."

The data used by eMarketer includes retail sales, travel sales, digital downloads purchased via any digital channel but excludes gambling and event tickets.