Twitter expects to post at least $1 billion in revenue by 2014 based on its expectations on the growth of its advertising business, says a Bloomberg report citing "sources with knowledge of the matter."

The growth is twice as fast as what analysts predict, according to Bloomberg. Twitter, however, could change or miss its forecast, the report today said.

The guidance would answer some critics questioning how Twitter would make money off its 140 million users. The company has increased its efforts to lure in marketers to the micro-blogging service, which relies on its users blasting out 140-character messages to each other.

Bloomberg cited EMarketer, which pegged Twitter's revenue in 2014 to be at $540 million.

But Twitter's ability to hit $1 billion in revenue by 2014 would still make it slower growing than Google or Facebook, the other major players on the Internet. It took Google five years to reach $1 billion, while Facebook hit the benchmark in six years, Bloomberg noted. Twitter will be eight years old in 2014.

The $1 billion is approximately what Facebook generated in the first quarter of this year.

Twitter aims to expand internationally, such as in Japan, as it looks to lessen its dependence on growth in the U.S. Still, a vast majority of users are in the U.S. At the same time, the company is looking to convince potential investors that it is able to capitalize on its large audience, an issue that has tripped up Facebook's early days as a public company.