Cheryl Cole has visited Sarah Harding in rehab.

The 'Promise This' singer is "pulling out all the stops" to help her Girls Aloud bandmate - who checked into an American treatment facility in Arizona earlier this month to receive help for depression and alcohol addiction - and the brunette beauty has even invited her to stay at her Los Angeles home to escape from the UK when she checks out.

A source told the Daily Star newspaper: "Cheryl is really concerned for her friend Sarah. She made time in her busy schedule to travel over to Arizona and visit her in the rehab centre.

"Cheryl feels really passionate about alcohol and drug abuse after years of worrying about her drug addict brother Andrew.

"She has told Sarah she is more than welcome to use her LA home as an escape pad when she comes out of rehab. A bolt-hole where Sarah can chill out and escape the London limelight and maybe try to save her relationship with Tom."

Sarah - who called off her engagement to DJ Tom Crane in the summer - has reportedly extended her stay in rehab and is unlikely to be out in time for Christmas.

Girls Aloud member Kimberley Walsh recently revealed 29-year-old Sarah is doing "really well" on the programme.

She explained: "I don't want to go into detail about Sarah, but she's doing really well."