Heavy is citing sources close to the bout.
Pettis was next in line for a UFC lightweight title shot but that was sidetracked when champion Frankie Edgar drew with Gray Maynard at UFC 125 earlier this month. Those two will meet again at a later date.
Instead of waiting for the winner of that bout, Pettis will not remain on the sidelines and will instead risk his No. 1 contender status.
Pettis is coming off a thrilling unanimous decision win over Ben Henderson at WEC 53 to claim the promotion's lightweight title. He gained fame for "The Kick" in which he jumped off the fence and delivered a kick that dropped Henderson to the canvas and likely sealed the fight.
Guida is coming off one of the biggest wins of his career, submitting former PRIDE lightweight champion Takanori Gomi in the second round at UFC 125.
He has won three in a row, ending all three fights by submission.
Pettis has won four straight.