Father Mike Manning has publicly acknowledged he had a sexual relationship with Nancy Kotowski, the superintendent of schools for Monterey County in Northern California and Manning's second cousin.
"The reality is I was living two lives: one as a priest who was vowed to celibacy and another life as a sexually active man in our sexual intimacy," Manning wrote to Kotowski, according to one excerpt.
In another, he says, "We've been such good friends, and there's a deep love we have for each other."
"The sexuality was secondary. It's very hard when you care for someone, but I love my priesthood more. I admit the fact of my sinfulness. I've done wrong. That's why I've stopped."
Manning has not commented on the authenticity of the excerpts.
He reportedly told colleagues that he ended his affair with Kotowski about three years ago -- two years before it was uncovered.
Kotowski called Manning her "soul mate" in an interview with the Monterey Herald. She also said she hopes the news of the affair will encourage changes to church rules about priests marrying.
Manning reached the decision to take a leave of absence in consultation with local church leaders, the Los Angeles Times reports.
He plans to remain in the ministry, church officials told the Times.
Manning hosts a weekly program on the Trinity Broadcasting network called "The Word in the World." It draws an audience of 200,000 households, according to Manning's website.
Manning has been hosting religious television shows since 1972.
He has also published several books, including an autobiography titled "On Camera and Off."