THE world's most famous investors are using the depressed markets to build up sizable stakes in US blue chips, which have been undervalued due to negative sentiment about the global economy.

Warren Buffett and George Soros are two of the oldest, richest and most savvy investors on Wall Street.

Now The Wall Street Journal's MarketWatch.com has tracked recent purchases by the pair.

Buffett's Berkshire Hathaway bought 27.3 million shares of Wells Fargo between January 1 and June 30, taking Berkshire's total holdings in the fourth-largest US bank to 411 million shares. Wells Fargo is Berkshire's second-largest position, behind Coca-Cola.

Berkshire also acquired 16.9 million shares of BNY Mellon Corporation in the first six months of 2012, while General Motors was a fresh investment as of March 31.

MarketWatch.com quoted fund manager Jeff Sica as saying Buffett was increasing his positions in industries that had received government support.

Soros, for his part, was back shopping at Wal-Mart during the second quarter, buying 4.8 million shares. Soros Fund Management had exited the stock a year ago, but the shares were trading as low as $57.18 during the second quarter, dogged by bribery allegations in Mexico. But the shares finished the second quarter up 14%, outpacing the 2% decline for the S&P 500.

MarketWatch.com noted that Wal-Mart is often seen as a safe bet for investors concerned about the global economy and the stock market. And Soros, Sica said, "has a negative outlook on the world economy".

Soros does appear to be playing some defence. Since January 1, his fund has purchased 8.6 million General Electric shares. In regulatory filings, his fund reported no position at the end of 2011.

* This article was first published in Sunday Times: Money & Careers