Despite having launched only a year ago, Square has shipped over 800,000 card readers to merchants and is currently processing over $2 billion in payments annually.

The company recently closed a $100M Series-C financing round led by Kleiner Perkins Caufield and Byers that valued the startup as a $1 billion Silicon Valley sensation..

In a posting on Virgin's blog site, Greg Rose, senior conent and marketing executive for Virgin Digital, says Branson took interest in Square's rapid growth and novel technology, in particular its free hardware that allows anyone to accept credit card payments anywhere, anytime.

Branson is quoted as saying: "I'm very passionate about helping people start and grow successful businesses, and Square is an incredible technology that inspires and empowers everyone to be an entrepreneur."

Square, which is planning to launch in international markets later this year, face stiff competition from Intuit, which announced a significant tie-up with US carrier AT&T for its GoPayment app and card reader yesterday.