Gary Barlow is desperate to duet with Agnetha Fältskog.

After co-writing a track for the Abba star's comeback album, 'A', released last month, the Take That frontman has begged the Swedish star to let him join her on stage in the future.

Speaking to Agnetha on a new BBC One documentary 'Abba and After', which airs next Tuesday (11.06.13), the 42-year-old singer says: ''One thing I'm really intrigued with is that how from today can I talk you into - and this may be a long thing, not to be decided today, maybe over the next few months - I would love, love the opportunity to do this track live.

''I'm prepared for no but I would love you to keep the door open. I think it would be unbelievable to see you sing live by yourself but I can take the credit with you.''

Despite Gary's enthusiasm, Agnetha - who has spoken openly about stage fright in the past - remains reluctant to accept his plea.

She replies: ''Can I say I will think it over? It isn't my strongest point.''

It isn't just stage fright that Agentha, 63, has been forced to overcome, as she previously admitted she needed to brush up on her vocals with singing lessons before recording her latest record.

She said: ''I could feel that I had lost some energy in my voice and you get easily tired. But everywhere it sounded good. It got better and better. I took some singing lessons too. That was mainly because I felt rusty. It was easy to get into it again.''