Burger King Holdings Inc
The company, which has a market capitalisation of about $2.3 billion (1.5 billion pounds), has been public since May 2006.
Famed for its flame-broiled Whopper, Burger King had previously been owned by private equity, which still hold a stake in the company. TPG, Bain Capital and Goldman Sachs
The Wall Street Journal previously reported the news, saying that Burger King has been in talks with private equity firms in recent weeks about a possible sale, and one interested firm was 3i Group Plc
The source who spoke to Reuters confirmed that one potentially interested party was 3i.
Burger King and 3i could not immediately be reached for comment.
Burger King in August forecast weak demand for its new fiscal year amid a struggling economy and said it was unsure how costs for key ingredients like beef would impact the company.
The company did not issue an earnings forecast for fiscal 2011 but said on Tuesday that high U.S. unemployment and government austerity programs in several European countries would weigh on same-restaurant sales.
The company, which competes with McDonald's Corp
Private equity firms have become increasingly active in the past few months, amid a spurt of M&A activity.
In August, Blackstone Group struck a deal to buy power company Dynegy Inc
Last month was the busiest August since 1999 in terms of the value of M&A deals struck.
(Additional reporting by Krishna N. Das in Bangalore; Editing by Mike Nesbit)