Sales of high-definition televisions are expected to increase dramatically over the next five years, accounting for 7 in 10 TVs sold in the United States by 2010, a market research firm said Thursday.

HDTVs, which made up 21 percent of overall TV sales in 2004, are expected to be in 63 percent of U.S. TV households by 2010, JupiterResearch said.

"After a slow start, HDTV is beginning to generate real consumer appeal," JupiterResearch analyst Joni Blecher said in a statement. "We attribute this to the increase availability of HD content as well as the growing number of HD sets available at retail."

In addition among the four available display technologies available, JupiterResearch expects LCD flat screens and projection displays to make up the majority of U.S. sales by 2020.

The other two display types are plasma and CRT.