SHANGHAI, July 4 -- TUDOU.COM, a leading Chinese video-sharing Website, launched an advertising system yesterday in its first step toward becoming profitable in the popular but costly business.

The ads - ranging from three to nine seconds - will be inserted into uploaded videos and the revenue shared with the video producers, according to the Shanghai-based company.

"It's difficult to give a forecast of ad sales at the very beginning," said Gary Wang, who founded the YouTube-like site.

In the worst case, it will take the business another three years before it turns a profit, he said.

The proportion for revenue sharing hasn't been worked out, Tudou officials said, adding that their ad system will offer an analysis of audience behavior on the site.

Tudou, which translates as "potato" in Chinese, has been a hot spot among China's rapidly growing video-sharing industry, drawing US$30 million in venture capital, the most in the sector.

But before the launch of the ad system it had no source of revenue. Site operators said their focus was to build Tudou into a popular platform and enhance user loyalty.

According to Nielsen NetRatings, Tudou had more than 30 million independent users as of May, accounting for around 30 percent of Chinese broadband Web users.

Ku6.com, which is also a leading video-sharing site in China, introduced a similar system last August and convinced several global brands to spend six million yuan (US$789,000), according to site founder Li Shanyou.