Feb. 14 (Bloomberg) -- Berkshire Hathaway Inc., the insurance and investment firm run by Warren Buffett, has built an $843 million stake in U.S. Bancorp.

During the first nine months of last year, Berkshire bought 23.3 million shares of Minneapolis-based U.S. Bancorp, accumulating 1.3 percent of the sixth-largest U.S. bank by assets. The purchases were disclosed for the first time today in filings with the U.S. Securities and Exchange Commission.

Berkshire also disclosed it bought 13.4 million shares of San Francisco-based Wells Fargo & Co. in the fourth quarter, bringing its stake in the largest bank on the U.S. West Coast to 6 percent.

Berkshire trimmed its holdings of Ameriprise Financial Inc. by almost 11 million shares in the fourth quarter, to 8.3 million shares, or 3.4 percent of the company. Buffett's holding company received 12.2 percent of the consumer financial services firm when it was spun off from American Express Co. in 2005. Berkshire is American Express's largest shareholder.

Buffett over four decades transformed Berkshire from a failing textile manufacturer into a $167 billion holding company by buying out-of-favor stocks and companies whose business and management he deemed superior. In the process, he became the world's second-richest man, behind Bill Gates. Because his decisions often are imitated, Buffett, 76, sometimes gets permission from the SEC to delay disclosing his investments.

UnitedHealth, Ingersoll-Rand

Berkshire disclosed a stake of 1.02 million shares of UnitedHealth Group Inc., the largest U.S. health insurer, and 636,600 shares of Ingersoll-Rand Co., the maker of Bobcat backhoes and Thermo-King refrigerated trucks. Berkshire's filing for the third quarter of 2006 didn't show either stock.

Berkshire sold 6.9 million shares of H&R Block Inc. in the fourth quarter, continuing to trim its stake in the largest U.S. tax preparer. Buffett's company owned 4.1 million shares as of Dec. 31, down from 16.1 million in the first quarter of 2006.

Holdings in home furnishings retailer Pier 1 Imports Inc. were reduced to 1.5 million shares from 3.3 million in the fourth quarter.

Also sold in the fourth quarter were Berkshire's remaining 745,700 shares of Target Corp., the second-largest U.S. discount retailer, 1.8 million shares of OSI Restaurant Partners Inc. and 677,700 shares of Sealed Air Corp.

To contact the reporters on this story: Josh P. Hamilton in New York at jphamilton@bloomberg.net; Zachary R. Mider in New York at zmider1@bloomberg.net.

Last Updated: February 14, 2007 20:18 EST