U.S. online TV and video services will generate revenues of US$7.9 billion by 2013, according to a forecast by Informa Telecoms & Media.

In 2007, the market value was over $1 billion, and by the end of 2008, it will reach $4.7 billion.

Although these figures include a la carte and subscription-based download fees, advertising revenue is expected to make up the biggest chunk at 63 percent of the global total in 2013, eMarketer reported.

"The Writers Guild strike brought much of Hollywood to a standstill for several months. The fact that revenues derived from online TV and video were at the heart of the dispute indicate just how important this sector has become," according to media research manager at Informa Adam Thomas.

Following the United States, the UK and Japan are the second and third largest markets, in terms of online TV and video revenues.

In 2008, revenues are expected to reach $842 million in the UK, and $605 million in Japan, according to eMarketer.