Shares of Sirius Satellite Radio took a 5.1% hit Monday after the pay-radio outfit slightly boosted its 2005 revenue forecast while sticking by its guidance of 3 million subscribers by year's end. The news disappointed Wall Street, resulting in the stock's slide.

Sirius disclosed the information in a regulatory filing Monday, revealing that, as of Thursday, it had 2.1 million subscribers, below where analysts expected the company to be at this stage. And while Sirius expects revenue of $230 million for the year, up from previous guidance of $225 million, that's still about $4 million below the average consensus of Wall Street analysts.

Sirius CEO Mel Karmazin is scheduled to speak at the annual Goldman Sachs Communacopia conference Wednesday in New York.

Subscription additions are "currently tracking below our third-quarter estimates for 383,000 net ads," Banc of America Securities analyst Jonathan Jacoby wrote. He added that Sirius should hit its 3 million target because of a new pricing promotion this month and a more aggressive ad campaign.

He added that a Ford Motor Co. factory installation program that began last month will help business. Jacoby expects Sirius and XM Satellite Radio to add 900,000 subscribers each in the holiday-fueled fourth quarter.

Sirius shares were off 36 cents to $6.69, while shares of XM also fell Monday, losing 1.6% to $34.87. XM recently reported having 4.4 million subscribers on its way to 6 million by year's end. In Tuesday trading, Sirius shares climbed 1.61% or 11 cents to $6.80; XM shares were trading at higher at $35.50.