SOCIETE Generale, France's second-largest bank by market value, bought a 37-percent stake in Rockefeller Financial Services Inc for an undisclosed price to add wealthy clients in the United States.

SG Private Banking and Rockefeller Financial Services, the parent of Rockefeller & Co, will work together to offer services to individuals and families with at least US$30 million to invest, said James McDonald, chief executive officer of Rockefeller & Co.

The deal is the second in North America this year for Paris-based Societe Generale's private-banking arm, following the February acquisition of CWM Group Inc, a Calgary-based wealth manager with US$637 million of assets. The US has almost 40,000 ultra high net worth individuals, those with more than US$30 million, according to a report last year by Cap Gemini SA and Merrill Lynch & Co.

"This is something of a coup for SocGen to secure the deal because if it had been known that Rockefeller was looking for an alliance there would have been a long queue," said Sebastian Dovey, director of consulting firm Scorpio Partnership Ltd in London. "Rockefeller is almost an entirely US book of business."

Societe Generale rose 1.97 euros, or 3.4 percent, to 60.11 euros by 12:50pm in Paris trading. The shares have declined 34 percent this year, valuing the bank at 35.5 billion euros (US$55 billion).

Societe Generale's private-banking arm has about 71 billion euros under management, while New York-based Rockefeller oversees almost US$30 billion. The French bank doesn't have an option to increase the stake, said Daniel Truchi, head of Societe Generale's private bank.

"Rockefeller had the intention to develop not only in the US, but worldwide, and we wanted to develop in the US," Truchi said in an interview with Bloomberg Television. "Overall, this makes quite a significant alliance." Rockefeller's clients can benefit from Societe Generale's knowledge of structured products, hedge funds and fund research, Truchi said. Rockefeller and the French company's private banking unit can develop global offers for very rich families, he said.

The deal comes less than five months after Societe Generale announced a 4.9-billion-euro loss resulting from unauthorized trading. The Paris-based bank was forced to raise 5.5 billion euros in a share sale to replenish capital after the loss and writedowns linked to the collapse of the US subprime market.

While the record trading loss did unsettle some of the private bank's clients, it didn't imperil the talks with Rockefeller, which began about a year ago, Truchi said.