Blockbuster will rent high-definition DVDs only in the Blu-ray format in 1,450 stores when it expands its high-def offerings next month, dealing a major blow to the rival HD DVD format.

The move, announced Monday, could be the first step in resolving a format war that has kept confused consumers from rushing to buy new DVD players until they can determine which format will dominate the market.

Blockbuster has been renting both Blu-ray and HD DVD titles in 250 stores since late last year and found that consumers were choosing Blu-ray titles more than 70 percent of the time.