(Reuters) - Warren Buffett's Berkshire Hathaway (NYSE:BRKa) Inc has applied to increase its ownership stake in Wells Fargo (NYSE:WFC) & Co past the 10 percent level that could prompt increased regulatory scrutiny, the Federal Reserve said on its website on Friday.
As of March 31, Berkshire was Wells Fargo's largest investor, with a 9.45 percent stake held mainly through subsidiaries, according to Berkshire and Reuters data.
Wells Fargo is based in San Francisco, and is the third-largest U.S. bank by assets.
Berkshire wants to add to its stake for investment purposes, does not have a dollar amount in mind, and does not plan significant changes to the bank's strategy or changes to its board, Bloomberg News reported, citing the June 14 application.
Buffett has long been a supporter of Wells Fargo, saying this year that it is "very well run" and a "terrific operation," and that Chief Executive John Stumpf has done a "fabulous job."
The Federal Reserve exerts special oversight when investors take large bank stakes.
In a September 2008 policy statement, the Fed said it often lets investors take double-digit bank stakes not designed to exert a "controlling influence," but would review any resulting business relationships "case-by-case."
The U.S. Treasury Department, meanwhile, has said it willnot deem a 10 percent stake to result in "control" of a big bankif an investor agrees in writing to limits on its involvement.
Berkshire also owns a nearly 16 percent stake in American Express Co (NYSE:AXP), Reuters data show.
In addition to investing in stocks, Berkshire also operates close to 90 businesses, including the Geico auto insurer, the BNSF railroad, Dairy Queen ice cream, and an array of food, apparel, energy and industrial companies.