The clip, which news reports said comes from a 2007 conversation Romney had with an Iowa radio talk show host, shows Romney engaging in a discussion on a variety of theological topics, Politico reported Monday.
"I'm not running as a Mormon," Romney said on the video. "And I get a little tired of coming on a show like yours and having it [be] all about Mormons."
In the video, Jan Mickelson, host of the conservative show on WHO in Des Moines, pressed Romney to explain how Mormons, adhering to religious texts, could also be pro-abortion, Politico said.
"Let me once again say, I understand my faith better than you do," Romney said. "You don't believe that, do you?"
Romney fielded the question, and then noted near the end of the interview his record as Massachusetts governor reflected his anti-abortion position.
"I was beaten up in Boston because I pointed out, time and again that I encouraged girls not to get abortions, that I told them to have adoptions," he said. "I have not done anything that in any way violates the principles of my church in that regard."
Romney became testy when Mickelson said he hoped they could have a more substantive discussion the next time Romney was his guest they.
"I don't like coming on the air and having you go after my church," Romney said. "You're trying to tell me that I'm not a faithful Mormon.
"I'm not running to talk about Mormonism," Romney said.