Regulators are starting to scrutinize Warren Buffett’s Berkshire Hathaway Inc. to determine whether it is important enough to the financial system to require Federal Reserve supervision, according to two people with knowledge of the matter.

The U.S. Financial Stability Oversight Council staff’s study of Berkshire doesn’t mean the panel is inclined to designate the Omaha, Nebraska-based company, said the people, who requested anonymity because the work isn’t public. Any decision could be months away, they said. The company’s reinsurance operation is the world’s fourth-largest.

The council, led by Treasury Secretary Jacob J. Lew, is evaluating which non-bank financial companies could threaten financial stability if they were to fail. The Fed can then impose stricter capital, leverage and liquidity requirements and demand stress testing for crisis scenarios.

Buffett didn’t return a message left with an assistant. Treasury spokesman Matt Bevens declined to comment. FSOC rules state that because of the “preliminary nature of the council’s evaluation,” it doesn’t disclose the names of companies until they are formally designated systemically important.

Since its first meeting in October 2010, the council has designated three systemically important non-bank financial firms: New York-based American International Group Inc.; Newark, New Jersey-based Prudential Financial Inc., and General Electric Co.’s finance unit. New York-based MetLife Inc., the largest U.S. life insurer, is in the final stage of review.

Potential Risks

The FSOC was created by the 2010 Dodd-Frank law to monitor potential risks to the financial system and prevent another crisis. Its voting members include Lew, Fed Chairman Ben S. Bernanke, and the chairmen of the Securities and Exchange Commission and Federal Deposit Insurance Corp.

The Financial Stability Board, the Basel, Switzerland-based body that’s responsible for strengthening global financial rules on behalf of the Group of 20 nations, has said it will make a decision in July on which reinsurers it considers systemically important.

Berkshire’s reinsurance operation, which includes General Re and National Indemnity Co., had net premiums of $16.1 billion in 2012, according to Standard & Poor’s. Munich Re is the largest reinsurer, followed by Swiss Re Ltd. and Hannover Re.

Some U.S. regulators want Berkshire to be analyzed before the FSB is close to making its decision, according to the people with knowledge of the matter.

Bank Holdings

Berkshire is also the largest stockholder in Wells Fargo & Co., the biggest U.S. home lender, and American Express Co., the No. 1 credit-card issuer by purchases. Buffett in 2011 injected $5 billion into Bank of America Corp., the second-biggest U.S. lender, after its stock slumped.

Buffett has sought to distinguish his firm from banks that were bailed out in the financial crisis on concern their collapse would deepen the recession.

“When the financial system went into cardiac arrest in September 2008, Berkshire was a supplier of liquidity and capital to the system, not a supplicant,” he wrote in a letter to shareholders in 2010.

To strengthen the financial system, Dodd-Frank places bank- holding companies with more than $50 billion in assets, such as Citigroup Inc. and Bank of America under increased Fed supervision.

Five Criteria

In addition, non-bank financial companies that have $50 billion or more in assets and meet any one of five other criteria, including having $30 billion in credit-default swaps linked to their debt, can be evaluated.

Berkshire had $458.1 billion of assets as of Sept. 30, the company said in a filing with the SEC. It had $31.4 billion in credit-default swaps linked to its debt as of Jan. 17, according to data from the Depository Trust & Clearing Corp.

Berkshire also had $5.8 billion in derivative liabilities as of Sept. 30, more than the $3.5 billion trigger set by the FSOC.

In its quarterly filing to the SEC, Berkshire said that even though Dodd-Frank “may adversely affect some of our business activities, it is not currently expected to have a material impact on our consolidated financial results or financial condition.”

Diamonds to Underwear

As Berkshire’s chairman and chief executive officer for more than four decades, Buffett, 83, built the firm from a textile maker into a company that sells insurance, hauls freight, generates electricity, manufactures chemicals and sells products from diamonds to underwear. The billionaire has used funds from insurance units including GEICO to buy stocks and make acquisitions.

Buffett has been a longtime supporter of President Barack Obama and served as an informal economic adviser. Obama awarded Buffett the Presidential Medal of Freedom in 2011 and called him “one of the most respected” men in the world.

Robert Benmosche, CEO of insurer AIG, has said he welcomes Fed oversight while highlighting that Berkshire hasn’t been given the same designation. AIG received a U.S. bailout in 2008 that it repaid four years later.

“They say big companies that are in the insurance business should be regulated, but I guess somehow they’re not,” Benmosche told an investor conference in June, referring to Berkshire. “They’re pretty big, the last time I looked.”

Berkshire is rated AA at Standard & Poor’s, the third-highest rating. That compares with the seventh-highest grade for AIG. Buffett’s firm had more than $40 billion in cash as of Sept. 30.

“We will never become dependent on the kindness of strangers,” Buffett wrote in the 2010 letter to shareholders. “Too-big-to-fail is not a fallback position at Berkshire.”

–With assistance from Dan Kraut in New York. Editors: Chris Wellisz, Dan Reichl