NEW YORK ? Burger King, the second-largest US hamburger chain, is in talks with private-equity firms for a potential sale, The Wall Street Journal reported Wednesday.

Among the interested firms is Britain's 3i Group PLC, the Journal said, noting that the talks had already lasted several weeks and that their status was unclear. Citing sources familiar with the matter, it noted that it was uncertain that the discussions would result in a sale.

Although it has been a public company since 2006, Burger King has already been through several buyout firms.

Faring worse than its bigger rival McDonald's in the wake of the financial crisis, Burger King last week reported a drop of 2.3 percent in its global sales for its 2010 fiscal year, compared to a 1.2 percent gain during the same period last year.

It also posted a 3.9 percent decrease in US and Canada sales, compared to a 0.4 percent increase in the same period last year.

"In fiscal year 2010, we faced sustained levels of high unemployment and a fragile global economy that combined made this one of the toughest operating environments in recent history," Burger King Chairman and CEO John Chidsey said in a statement.

The fast-food chain currently has a market capitalization of about 2.26 billion dollars and operates over 12,000 restaurants worldwide in more than 75 countries.

Among its portfolio companies, 3i counts luxury lingerie retailer Agent Provocateur Ltd., European juice and soft drinks maker Refresco and China's Little Sheep restaurant chain.