Biden didn't give a firm answer when asked in a CNN interview whether he plans to run for president in 2016.
"There may be reasons I don't run but there's no obvious reason for me why I think I should not run," he said.
O'Brien poked fun at Biden's use of a double negative in a fake campaign ad he aired on TBS' "Conan" this week, the Hill reported.
"Joe Biden has served this country for over 40 years so when he says he's not uninterested in seeking the presidency, it shouldn't be a no-brainer to refuse to disbelieve him. Biden won't just not undermine the economy. He would oppose all efforts to negate unemployment. He's on the record against not blocking anti-progressive legislation that doesn't not destabilize working families. Joe Biden -- no compelling reason not to vote for the opposite of his opponent," the narrator on the fake ad said.
"I'm Joe Biden and I don't not fully and especially not partially endorse this message," an actor pretending to be Biden said at the end of the ad.
Biden told CNN he'd probably make a decision about running for president during the summer of 2015, the Hill said.