According to Live 8 organizer Bob Geldof, one woman stands in the way of a "Girl Power" revival.

Within hours of Geldof's May announcement that he'd organized a star-crammed, five-concert sequel to his landmark 1985 Live Aid concerts, there's been persistent speculation that Spice Girls would reunite for a July 2 Live 8 performance.

But are Scary, Posh, Baby, Sporty and Ginger set to mend fences and grace a London stage to raise awareness of poverty in the developing world?

Not just yet, Geldof said -- but he's determined to try and make it happen. It all hinges, he explained, on one of the pop act's members.

In an interview on Channel 4's "Richard & Judy" (the U.K.'s answer to "Regis and Kelly") on Monday, the former Boomtown Rats leader said the only person holding up the regrouping is Melanie Brown, better known as Scary Spice.

He told the show's hosts that Brown was having "difficulty" agreeing to the Live 8 regrouping, but that he's still hoping to convince her to hop aboard the reunion train. Geldof claims that Mel B has been working in California -- he didn't say on what -- and that the singer's not keen on "going back to something she did in the past."

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Geldof promised to reach out to Mel B this week, BBC News reports, but he plans to back off if she refuses. "If she can't do it, she can't do it," he said. The Live 8 mastermind also shot down suggestions that Spice Girls re-form sans Scary, saying, "It's got to be all or nothing."

When Geldof first revealed plans for the Live 8 concerts (see [article id="1503200"]"50 Cent, Jay-Z, Mariah, U2, Coldplay On Board For Massive Live Aid Sequel"[/article]), he hinted at there being a strong possibility that the Spice Girls would re-form for the event. "I spoke to them this morning," he said, according to BBC News. "It looks very good. That's all we can say."

MTV will be bringing you all of the Live 8 action -- including live performances, interviews and more -- starting at noon ET on July 2. More details will be announced soon.

Get involved: Learn about the poverty crisis in Africa, the proposed solutions, and how you can help. Plus find all of our coverage of the international Live 8 concerts and more at our thinkMTV Live 8 hub.