NEW YORK?Burger King said Thursday it had accepted a $4-billion takeover bid by a little known investment firm, as the fast food chain tries to close the gap with leader McDonald's and expand overseas.

While the second largest US fast food chain moves into private hands following its acquisition by 3G Capital, Burger King fans can expect to find "The Whopper" in more countries outside the United States.

The takeover by the private equity group, which is backed by Brazilian investors, comes at a key moment for the fast food chain.

Burger King was taking a longer time to recover from the economic crunch than McDonald's as its traditional client base ? young, male and in most cases a minority ? was more exposed to the recession, said Meeschaert New York market analyst Gregori Volokhine.

"McDonald's has a family-oriented image which appeals to a much larger segment, so naturally Burger King was harder hit by the economic crisis," he told AFP.

McDonald's sales reached $22 billion in its last fiscal year, with a $4.3-billion profit, while Burger King boasted $2.2 billion in sales with a $186-million profit.

But with 3G Capital also set to assume Burger King's debts, the company's return to private ownership could bode well in its competition against McDonald's, said Volokhine.

"Burger King has suffered so much from the comparison with McDonald's, being under the public's eyes, that as a private company it can be a different ball game... It is very hard for a public company to compete against a giant."

Burger King recently stated it will stick to its long-term goal of expanding its operations outside the United States to 55 percent, compared to 35 percent today.

Analysts at Citi Group said the acquisition could offer some tailwind to the plan, but that it would still take Burger King 10 to 15 years before it reaches this mix.

The fast food chain, which today operates 12,150 restaurants across the world, saw its share shoot up nearly 25 percent to 23.43 on Thursday following the announcement of its acquisition.

Burger King was introduced to the stock market in 2006, four years after TPG, Goldman Sachs Capital Partners and Bain Capital bought it for $1.5 billion from British spirits group Diageo.

3G Capital agreed to buy all of Burger King's stocks at $24 per share in cash, representing a 46 percent premium. The deal was unanimously approved by Burger King's board of directors and is expected to be wrapped up by the end of 2010.

Following the announcement, international rating agency Moody's announced that it might cut back Burger King's rating as the acquisition is set to substantially deepen its debts.

"We look forward to partnering with 3G Capital, whose proven track record as an investor, together with its financial and consumer brands experience, will serve to further strengthen the company, our restaurants and franchisees worldwide," Burger King CEO John Chidsey said.

Chidsey will remain through the transition period in his current capacity and become co-chairman of the board following the acquisition alongside 3G Capital managing partner Alex Behring.