Mel B is having "difficulty" agreeing to a Spice Girls reunion for the Live 8 concert, organiser Bob Geldof has said.
'Scary Spice' Mel B is currently working in California
But Geldof is still hoping to persuade her to come on board for a comeback show in London's Hyde Park on 2 July.
He told UK TV show Richard and Judy that Mel B was working in California but also "has difficulty going back to something she did in the past".
He added: "I'll call her during the week and if she can't do it, she can't do it."
'All or nothing'
Geldof told the Channel 4 show: "No, it's got to be all or nothing," when co-host Richard Madeley suggested the band reform without 'Scary Spice'.
Madeley then said: "Well, I know her mum. I'll call her up for you!"
When Geldof revealed plans for the Live 8 concerts at the end of May, he said there was a strong possibilty that the Spice Girls would reform for the event.
"I spoke to them this morning. It looks very good. That's all we can say," Geldof said at the Live 8 launch on 31 May.
British and African musicians, including Damon Albarn and Beth Orton will be boarding the London Eye from Tuesday at 1930BST in an event to mark the G8 summit and raise awareness of Africa.
Flight 5065 will see a pair of musicians play in each of the capital's 32 pods to an audience of 20 people per pod.