Madonna Still 'Weak,' Slow Recovery Makes Celebration World Tour Kickoff Uncertain

Madonna is supposed to hit the stage in 10 days for the beginning of her much-anticipated world tour, but based on the information we're getting about her recovery from a serious infection, it's not looking good.

Sources with direct knowledge tell TMZ ... Madonna's recovery is not going as quickly as she expected. One source says she's still "weak and very tired," spending a significant amount of time in bed.

We're told the 64-year-old megastar is not waiving the white flag and postponing the tour, at least not yet. She's been mum on the subject, at least with most of the folks with whom she interacts.

As we reported, a bacterial infection landed her in the ICU for several days, after collapsing a week ago Saturday. She had a fever for more than a month, but kept it a secret, fearing it could derail her "Celebration" tour.