Buffett told a press conference here Monday he had offered support to both Obama and Democratic rival Hillary Clinton but that since it appeared Obama would win the party's nomination, "I will be very happy if he is elected president.
"He is my choice," Buffett said.
Commenting on the US economy, the 77-year-old investor who is known as the "Sage of Omaha," stressed that fiscal, monetary and trade policies were of great importance.
"I think that the US has followed and is following policies which will cause the US dollar to weaken over a long period of time," he said.
After voicing support for Obama, Buffett nonetheless noted the US economy had managed to do "awfully well" despite a depression, two world wars and many financial crises.
"They say in the stock market ... buy stock in a business that's so good that an idiot can run it because sooner or later one will," he added.
"Well, the United States is a little like that. We can take a little mis-management from time to time," Buffett said.
The chief executive of Berkshire Hathaway, a holding company with 76 businesses, also said he was ready to add one or two more, on condition they were well-run and had annual pre-tax earnings on the order of 50 million euros (78 million dollars), he added.
"The bigger the better," Buffett said.
Almost all of his companies are in the United States but after investing in the Israeli industrial group Iscar, he was visiting Germany, Switzerland, Spain and Italy to spread the word that European groups were also welcome to give him a call.
"I kind of go the the office everyday and wait for the phone to ring and hope it isn't a wrong number," he quipped to describe his strategy of letting companies come to him rather than searching them out.