The team confirmed the move Thursday. The deal, a source told ESPN's John Clayton, is for one year and worth around $4 million.
Porter's representatives are reviewing the language of the deal and hope to sign it by Friday.
Porter, 25, started 39 of the 43 games he played for the Saints since being drafted in the second round of the 2008 draft.
In 2011, he had 52 tackles and an interception in 14 games.
He has seven career interceptions and picked off a career-high four passes in the Saints' 2009 championship season. He returned an interception of Peyton Manning -- now the Broncos' starting quarterback -- 74 yards for a touchdown in the Super Bowl, sealing the victory for the Saints over the Colts.
Information from ESPN senior NFL writer John Clayton and ESPN.com AFC West blogger Bill Williamson was used in this report.