Fox News's Chris Wallace, moderator of the final presidential debate between Donald Trump and Hillary Clinton on Wednesday, says his job at the match-up isn't to become a "participant."

In an interview with colleague Bret Baier aired on "Fox News Sunday," Wallace — the first Fox moderator to do a general election debate — said, "Basically, you’re there as a timekeeper."

"An interview, it's you and the candidate and you're the person holding them to account," he said. "This is a debate. And, you know, they're both going to be on the stage. If I think there's a need for me to intervene, I will, but I would prefer not to."

"You're not a participant," he added. "You're there just to make sure that they engage in the most interesting and fairest way possible.And I take it very seriously. It's not a TV show that we're doing. "

NBC's Lester Holt and ABC's Martha Raddatz faced some criticism for interacting with the candidates too often in the first and second debates.

"Look, there's a lot of pressure," Wallace said. "We've seen … previous moderators get criticized, and at certain points I've had to remind myself, this may be a once in a life opportunity, so have fun — to the degree you can stop biting your nails, have fun with it."

He said he thinks his late father, the 21-time Emmy-winning journalist Mike Wallace, would be proud.

"I also think that if he could, he'd try to steal it from me," he joked. "But once he learned he couldn't, he'd say, 'that's my boy.'"

The 90-minute debate will be held in Las Vegas.