(Corrects headline and first bullet to clarify dollar figures are market valuation, not IPO valuation)

Daily deals website Groupon could be valued at as much as $25 billion in an initial public offering, Bloomberg reported on Thursday, citing two people with knowledge of the company's discussions with banks.

The offering may happen this year and would likely value Groupon at a minimum of $15 billion, the sources told Bloomberg.

Groupon did not immediately respond to requests for comment on the report.

Groupon founder and Chief Executive Andrew Mason told Reuters in January that the company was considering a public offering and was in talks with bankers, but had had yet made a decision about whether to proceed.

A source told Reuters in January that a Groupon offering would be meaningfully sized.

The two-year-old start-up rebuffed a $6 billion advance from Google Inc late last year, according to media reports. Over the course of 2010 it grew to 50 million users, from 3 million, in 500 cities in 40 countries.

(Reporting by Maria Aspan; editing by John Wallace)