\"I'd be lying if I said that I knew I was there,\" he told Colbert on \"The Late Show.\" \"I'm being completely honest.\"

Biden, still wrestling with the death this spring of his eldest son, told Colbert that any person running for president should commit themselves fully to the cause -- and he wasn't yet sure he could make that obligation.

His comments in a midsized auditorium at the Ed Sullivan Theater came on Colbert's third show since assuming the role as host of \"The Late Show\" following the departure of David Letterman. The interview was emotional, serious, and largely focused on Biden's recovery from his son's death, with Biden speaking at length about how his faith carried him through the turmoil.

But amid intense scrutiny of the vice president as he decides on a presidential run, Biden said he wasn't sure if he was in the emotional place to become a presidential candidate again.\"Nobody has a right in my view to seek that office unless they're willing to give it 110% of who they are,\" he said. \"And I am -- as I said I'm optimistic, I'm positive about where we're going -- but I find myself -- you understand it -- sometimes it just overwhelms you.\"Biden is expected to make his decision whether to run for president in the coming weeks, but he he has questioned aloud whether he has the \"emotional fuel\" for a campaign to dislodge Hillary Clinton from the pole position in the Democratic race.