Plans for Britney Spears [ tickets ]' comeback tour are expanding, with the resurgent pop star rolling out encore performances in a half-dozen cities as she gears up for a 2009 roadtrip behind her recently released album, "Circus."

On the heels of strong intitial on-sales over the weekend, Spears' schedule has been bolstered with second nights in Newark, NJ; Toronto; Los Angeles; Anaheim, CA; Rosemont, IL; and Uniondale, NY. Details are shown below.

As previously reported, Spears' forthcoming run--dubbed "The Circus Starring Britney Spears 2009 Tour"--is set to launch March 3 in New Orleans and visit 27 cities across the US and Canada through late April. Special guests The Pussycat Dolls will open the shows.

Spears plans to begin rehearsing for the tour after the holidays with director and Emmy-winning choreographer Wade Robson, according to a press release. Last week, she gave fans a glimpse of things to come with a live performance on ABC-TV's "Good Morning America."

"Circus," Spears' sixth studio effort, surfaced last month. The album's lead single, "Womanizer," recently made a one-week leap from No. 96 to No. 1 on The Billboard Hot 100, setting a record for biggest jump in that chart's history, according to the magazine. The song is streaming at Spears' MySpace page.