Oil prices could hit $100 a barrel by the end of next year, U.S. oil magnate T. Boone Pickens said on Tuesday, revising his previous forecast which said they would reach that level as early as this year.

"I think you could very well be at $100 a barrel by the end of 2016," the 86-year-old billionaire and chair of BP Capital told an audience of about 100 at the Commonwealth Club of California in San Francisco.

Oil prices have fallen sharply amid weaker Asian and European demand and a boom in North American production. U.S. crude futures CLc1 have dropped more than 60 percent since highs last summer and were at around $47.40 a barrel on Tuesday.

Pickens said the idea of "peak oil" - the point in time at which oil production will go into an irreversible decline - shouldn't be dismissed on account of the increase in U.S. production. Other regions are seeing their output decline, he said.

A lifelong Republican, Pickens said he would support Jeb Bush if he decided to pursue the party's nomination in 2016, as is widely expected.

"The Republicans will win in 2016," said Pickens, who has donated heavily to Republican presidential candidates in the past, including Jeb's brother, former President George W. Bush.