The announcement is scheduled to be made Tuesday in Washington D.C.
The announcement first was reported by The Politico. Click here to read the blog posting on The Politico.
Thomspon, speaking Monday to reporters in Indianola, Iowa, initially was cool to talking about the endorsement before it was announced, but shortly found a way to talk about the benefits.
"I would not ever make any statement about anybody endorsing me until they've endorsed me...I can't respond to the word on the street," Thompson said.
But answering a follow-up question what a pro-life group's endorsement would mean, Thompson said: "I've had a 100 percent pro-life voting record in the United States Senate ... and I think they know that. And that's the way I'd govern if I was President. ... So it (the endorsement) would be a perefctly natural thing and very helpful to me I would think."
The endorsement follows a series of heavy-hitting endorsements for Republicans from conservative groups in recent days, and is an important grab for Thompson who has been struggling to make his late-bloomer campaign more competitive.
Last Wednesday, GOP frontrunner Rudy Giuliani snagged an endorsement from evangelical Christian leader Pat Robertson: an announcement that drowned-out what would have been a big nod for Arizona Sen. John McCain on any other day, the backing of Sen. Sam Brownback, R-Kansas. Brownback has long been a favorite of conservative Christians, and threw his support behind McCain after dropping his own candidacy last month.
And earlier in the week, former Massachusetts Gov. Mitt Romney received an endorsement from another conservative leader, Paul Weyrich, founding president of The Heritage Foundation and cofounder of the Moral Majority.
Thompson's voting record is strongly in favor of abortion opponents, but his response to a 1994 questionnaire that surfaced earlier this year on abortion rights raised some questions over how strongly he stood against abortion.
Responding to Project Vote Smart prior to his 1994 election win, Thompson said he supported legal abortion in the first trimester in all cases — a view not held by abortion opponents.
But Thompson's other responses were more favorable: he said he believed there should be parental notification for mothers under the age of 18 who are seeking abortions; he supported state-imposed waiting periods and opposed federal funding for clinics that provide abortions. He also said abortions should not be covered under federal health care plans, and states, rather than Congress, should control abortion laws.
As a lawyer, Thompson also once represented an abortion-rights group, the the National Family Planning and Reproductive Health Association.
IN an August interview with The Associated Press, Thompson said his work to represent the group was separate from his beliefs.
"It has nothing to do with one's political views," he said. "Lawyering is a profession and it's also a business."
FOX News Carl Cameron and Cristina Corbin contributed to this report.
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