The demand for television delivered to cell phones is uncertain and mobile carriers could get hurt if they invest too much money in it, a study released Thursday by Strategy Analytics claims.

Such services are being trialed in various parts of the world, most notably Korea, but service isn't expected in Europe and North American for as long as two years, the study notes. Still, the report warns that phone vendors and wireless operators who are bullish about mobile TV should proceed with caution.

"Consumer demand for mobile TV remains highly uncertain, and we remain unconvinced that consumer appetite for mobile TV services exists outside of niche segments," Phil Taylor, director of Strategy Analytics' global wireless practice, said in a statement.

Instead, wireless operators should test the market first with streaming video services, the report said. Verizon Wireless recently launched its V CAST service, which is heavy on streaming video.

David Kerr, a Strategy Analytics vice president added that the technology roadmap for mobile TV remains uncertain and that the relative scarcity of wireless spectrum may also hurt adoption.