Sirius Satellite Radio Inc. (SIRI) Monday said it recently surpassed 4 million subscribers to its nationwide pay radio service.

Sirius, No. 2 in the nascent market to rival XM Satellite Radio Inc. (XMSR), had previously said it ended 2005 with 3.3 million subscribers, an increase of 2.2 million, and expects to end 2006 with more than 6 million subscribers.

XM in February said it has more than 6 million subscribers and expects to reach 9 million by the end of the year.

Both services offer continuous sports, talk, and entertainment programming, including dozens of commercial-free music stations, all for about $13 a month.

Sirius' news follows its announcement on Friday that it reached a deal with music companies Warner Music Group Corp. and Vivendi Universal SA's Universal Music Group to allow their songs to be played on a new radio unit that can store songs for future playback.

Under the pact, Sirius will pay a fee for each unit of its new S50 radio device that it sells, according to officials from the three companies.

Shares of Sirius rose 31 cents, or 6.3 percent, $5.20 in early trade on Nasdaq. XM shares rose 42 cents, or 2 percent, to $21.16.