There's just no stopping Susan Boyle on the U.S. pop chart.

Her debut album I Dreamed a Dream claimed the No. 1 spot on the Billboard 200 for a fourth week in a row Wednesday, denying Alicia Keys a shot at the top.

It sold 661,000 copies during the week ended December 20, according to Nielsen SoundScan, taking its total to 2,465,000 copies -- the second-best selling album of 2009. Only Taylor Swift's Fearless -- a 2008 release with 2,933,000 copies sold this year -- is standing in its way. And with two weeks left in the 2009 tracking year, anything is possible.

Keys' The Element of Freedom debuted at No. 2 with 417,000. All four of her previous albums -- three studio sets and an Unplugged release -- started at No. 1. Her last effort, As I Am, kicked off with 742,000 copies during Thanksgiving week of 2007.

However, Keys still has a chance of eventually reaching No. 1. The set could rise to the top next month when (and if) the Boyle hysteria dies down.

The second-biggest new arrival was Robin Thicke's Sex Therapy: The Session, which began at No. 9 with 123,000. It's the singer's third top 10 set in a row, following The Evolution of Robin Thicke (No. 5 in 2007) and Something Else (No. 3 in 2008). The latter album opened with 137,000 copies.

The only other debuts on the Billboard 200 were all the way down at Nos. 172 (the Avatar soundtrack) and 198 (Phil Vassar's Traveling Circus).

After five weeks at No. 2, Andrea Bocelli's My Christmas slipped to No. 3 with 390,000. The seasonal set has blown through 1.9 million copies and is now Bocelli's third-best seller after 1997's Romanza (4.2 million) and 1999's Sogno (2.5 million).

Swift held at No. 4 as Fearless shifted 239,000, while Carrie Underwood's Play On (153,000) and Lady Gaga's The Fame (141,000) were also unchanged, at Nos. 5 and 6, respectively.

Michael Buble's Crazy Love rose two places to No. 7 with 140,000 copies, surpassing the one-million mark. Justin Bieber's My World held at No. 8 with 127,000.

The second volume of the Glee TV soundtrack fell seven places to No. 10 in its second week with 111,000.

Overall album sales totaled 15.14 million units, up 26% compared to last week, but down 12% compared to the same sales week of 2008. Year-to-date sales stand at 357.5 million, down 13% compared to the same total at this point last year.