Madonna joins Twitter for a day, invites Justin Beiber to join the tour.

American singer and actress Madonna has joined Twitter... for a day!

The veteran musician has reportedly jumped onboard the social networking bandwagon to promote the release of latest (12th) studio album - MDNA.

As expected, her many millions of fans have been super excited to see their star singer on the service and have been tweeting her with questions and comments.

"Madonna joins Twitter for one day only to answer fan questions and celebrate the release of her MDNA album. Got a question? #AskMadonna," read a statement on Madonna's Web site.

Incidentally, the singer, when asked what she thought of Justin Bieber, by a common fan, replied saying he was "awesome".

"He's awesome. I'm a huge fan. I love it when he raps," Madonna tweeted, adding, "Come and join me on stage when I'm on tour when we are in the same city and congrats on your new single."

Bieber's reply: "@MadonnaMDNAday... seeing that is a huge honor. Yours is a career artists dream of."

So... could there be something in the works?