The 'Ordinary People' singer posted an open letter on his website on Wednesday to explain why he is pushing all but one concert into 2013.
"We announced the dates before we'd finished the album because we were sure we'd finish the album in time," Legend explained.
"Unfortunately, while the creative process has been exciting and I'm pretty certain we're going to deliver the best album of my career so far, the timing hasn't adhered to the schedule I originally envisioned.
"In other words, we're not done with the album."
Legend also apologised for disappointing fans who had spent "hard-earned money" on tickets to his shows.
He is still scheduled to play in Atlantic City on October 27.
Legend's most recent record Wake Up!, a collaborative album with The Roots, was released in September 2010.
Watch John Legend perform 'Ordinary People' below: