How I Met Your Mother producer Craig Thomas revealed this week that the current season is being written "like it's the end", but added that writers are preparing for an additional ninth season as a back-up plan.
Harris - who plays Barney Stinson on the CBS series - has now admitted that it's extremely unlikely that a ninth season will actually come to pass.
"Our contracts end at [season] eight, so it's one of those, you know, if they wanna do nine, they're welcome to, but we have a lot of other things," Harris told Access Hollywood.
He went on to say: "Cobie [Smulders] has got The Avengers that just made a billion dollars, Jason [Segel] makes a ton of movies, I'm anxious to move east and Josh [Radnor] is directing and acting in movies as well. So, we all are anxious to move forward."
Harris added that the only way an additional How I Met Your Mother season will go forward is with a financial raise for the cast.
"I think the only way I think a season nine or any longer would happen would be [if it were] financially right - that's the reality of it," he explained.
"We love the show, we love doing it - eight years is a long time and we're as happy a family as we've ever been."
Earlier this week, CBS announced that Reno 911 star Joe Lo Truglio will be a guest star on an upcoming season eight episode.
How I Met Your Mother returns on Monday, September 24 at 8/7c on CBS.