• Warren Buffett has funneled $2.2 billion into Wells Fargo & Co - his company's biggest stock
• The CEO of investment firm Berkshire Hathaway has also backed US Bancor and New York Mellon

By Helen Collis

PUBLISHED: 10:19 EST, 16 August 2013 | UPDATED: 10:41 EST, 16 August 2013

One of the world's richest men has put his faith in three US banks by investing  $3 billion (£1.9 billion) in them.

Warren Buffett, who is chairman, CEO and primary shareholder of investment firm Berkshire Hathaway, has bought an additional 4.96 million shares in Wells Fargo & Co worth $2.2 billion (£1.4 billion).

Wells Fargo is the investment firm's largest stock holding which swelled 1.1 per cent after it increased its stake, which now totals 463.1 million shares.

Meanwhile, the business tycoon has also funneled $745 million (£477 million) into US Bancor and $161 million (£103 million) into New York Mellon, according to CityWire news service.

The veteran investor has previously spoken out about his confidence in US banks as a solid investment. In January, in interview with Bloomberg, he highlighted three reasons to back them.

Quoted in Forbes magazine, he told Bloomberg: 'The banks will not get this country in trouble, I guarantee it.'

He continued: 'The capital ratios are huge, the excesses on the asset side have been largely cleared out… we own bank shares and I personally own stock in banks… I do not see problems in these things.'

Yesterday, alongside the banking investments, the 82-year-old's firm also reported buying a 17.8 million-share stake in Suncor Energy Inc, Canada's biggest oil and gas producer which has a large presence in the Alberta oil sands.

That stake was valued at $524 million (£336 million) at the end of the second quarter.

It also reported a small, 547,312-share stake in Dish, the satellite TV company run by billionaire Charlie Ergen, valued at $23.3 million (£15 million) on June 30.

The changes were disclosed in a U.S. Securities and Exchange Commission filing made public on Thursday, which detailed $89 billion (£57 billion) of Berkshire equity investments, mostly listed on US exchanges, as of June 30.

US regulators require large investors to disclose their stock holdings every quarter, and the disclosures can offer a window into their strategies for buying and selling stocks.

Shares of companies often rise after Berkshire discloses sizable new investments because investors try to copy Buffett, the world's fourth-richest person according to Forbes magazine.

Meanwhile, speculation has been mounting since May as to who will succeed the billionaire tycoon at the helm of the investment firm.

Buffett announced at the annual Berkshire Hathaway shareholder meeting that he knows who his successor is, but he declined to name the person or persons.

Tracy Britt, 28, a Harvard graduate who has been mentored by Mr Buffett since 2009, is considered the investor's right-hand man and some say has a good chance of stepping into his shoes.

After just four years, she has become a trusted confidante of the billionaire and chairwoman of four of his companies, which bring in $4 billion (£2.56 billion) combined annually.

In 2007, in a letter to shareholders, Buffett announced that he was looking for a younger successor, or perhaps successors, to run his investment business. Speculation is mounting that Britt is that successor.