An auction run by Goldman bankers has just gotten under way, the sources said. Potential buyers are said to include rival brokers Alliant Insurance Services Inc., owned by private equity giant Blackstone Group LP, and Hub International Ltd., which Apax Partners LP and Morgan Stanley control.

USI also could draw interest from Carlyle Group, Hellman & Friedman LLC, Kohlberg Kravis Roberts & Co. LP, and J.C. Flowers & Co. LLC and other PE shops that have invested in the sector.

How much it might sell for isn't clear. The Briarcliff Manor, N.Y.-based broker hasn't released financial results since Goldman Sachs Capital Partners bought USI in a $1.4 billion take-private in May 2007. Goldman declined to comment on the sale.

However, a PE banker at another bank put USI's annual Ebitda at around $190 million. This figure suggests USI could fetch as much as $1.8 billion, given that publicly traded insurance brokers such as Aon Corp. and Marsh & McLennan Cos. trade at 8.5 to 9.5 times Ebitda.

Five years ago, GS Capital Partners paid about 9.7 times USI's Ebitda of $150 million. It sank about $485 million of equity into its purchase.

USI sells property and casualty insurance and employee benefits products to small and midsized business. Annual revenue is close to $700 million, according to the company's website. The company employs 4,000 people in 82 offices in 24 states.

In June 2009, USI raised additional bank debt to retire about $168 million face value of its $400 million of high-yield bonds at a fire-sale price of around 60 cents on the dollar.

In October 2010, when Moody's Investors Service issued its last report on USI, total debt stood at $1.1 billion.

Affirming an overall credit rating of B3, Moody's at the time pointed approvingly to USI's top-10 industry ranking and its ability to cross-sell a variety of products to its clients.

"These strengths," the agency observed, "are tempered by the company's high financial leverage and by the headwinds of soft pricing in commercial P&C insurance and a sluggish U.S. economy."