A group of investors seems to be making a new bet on Square.

The mobile payment start-up is close to raising another $200 million, according to The New York Times, bringing its implied valuation to a cool $3.25 billion. Unnamed sources told the Times that Suhail Rizvi, the head of a private equity firm that has made investments in Twitter and Playboy, will lead the financing round.

The brainchild of Twitter co-founder Jack Dorsey, Square has been seen as an industry darling: It received a $100 million funding round last summer, and $240 million a few months before that, the Times notes. And its growth has been strong; the paper reports that users doubled to 2 million in the first half of 2012, with Square on pace to process $6 billion in transactions a year.

But Square is far from a clear winner in the highly competitive (and incredibly fragmented) mobile payment space. Google, Intuit, and eBay's PayPal are three big names battling for supremacy, while other smaller companies, like mPowa and PayAnywhere, are also vying for a slice of the mobile payment pie.   

According to NPD data tracking mobile shopping and transactions on Android phones, PayPal is the current industry leader, accounting for 13% of users who engaged with a mobile payments tool in May.  No other companies had more than a 5% share of the market. (The NPD research didn't cover iPhone users.)

Because several other companies have released miniature credit card readers, the Times suggests that Square’s future success may rely on its ability to advance more differentiated technologies, like its new app, Pay With Square. (Times tech reviewer David Pogue is a fan.) The app allows consumers to pay for goods simply by speaking their name--no credit card swipe required--and the company told the paper that more than 75,000 vendors have signed up for the app so far.