In the clearest signal yet that he is actively considering a run for president in 2016, Vice President Biden will headline Iowa Sen. Tom Harkin's annual steak fry next month, according to sources briefed on the event.

Joe Biden, left, is going to Iowa.

"The vice president accepted Senator Harkin's invitation to attend the steak fry this year," said a source in the vice president's office. "It has been a long-standing commitment after the vice president was unable to attend last year."

The news was first reported by Jonathan Martin of the New York Times.

Harkin's steak fry has been a rite of passage for many Democratic presidential wannabees. It was headlined in 2012 by Maryland Gov. Martin O'Malley, who is viewed as a presidential aspirant in 2016. San Antonio Mayor Julian Castro will also be speaking at this year's event.