Warren Buffett has criticised the protectionist stance taken by some US politicians to state-run investment funds from Asia and the Middle East.
Warren Buffett's success means his words are closely followed
These investors have taken stakes in Western banks and other businesses recently and concern has arisen that their motives are not just commercial.
But the billionaire investor said they were attracted to the US by the weak dollar - not for "some nefarious plot".
His comments come amid growing calls for them to become more transparent.
US firms that have recently attracted interest from sovereign wealth funds include Wall Street giant Merrill Lynch and Citigroup.
But in an annual letter to shareholders of his Berkshire Hathaway investment firm, Mr Buffett argued that the moves were not surprising given the declining value of the dollar, which has been battered by an "unsustainable" trade deficit and national debt.
"This is our doing, not some nefarious plot by foreign governments," he said.
"Our trade equation guarantees massive foreign investment in the US. When we force-feed $2bn (£1bn) daily to the rest of the world, they must invest in something here. Why should we complain when they choose stocks over bonds?"
Separately, he announced plans to look for more opportunities abroad to grow earnings for Berkshire Hathaway to offset the effects of the weak dollar, while reporting a 20% rise in 2007 net income to $13.2bn.
The profit growth came even as falling insurance rates sent fourth-quarter profits tumbling to $2.95bn from $3.58bn a year earlier, as premiums fall from their highs following Hurricane Katrina in 2005.
Nicknamed the "sage of Omaha" because of his success with investments, Mr Buffett, 77, is one of the richest men in the world.
He has stakes in a range of companies, including Coca-Cola, Proctor & Gamble and Tesco.