Republican presidential candidate Donald Trump waves as he meets with attendees during a campaign stop at Farmington High School on Jan. 25 in Farmington, N.H. (John Minchillo/AP)

Ten antiabortion activists wrote in an open letter Tuesday that Iowa caucus-goers should "support anyone but Donald Trump," who they say cannot be trusted to defend unborn children and has not respected women.

"America will only be a great nation when we have leaders of strong character who will defend both unborn children and the dignity of women," the letter states, according to a version shared with The Washington Post ahead of its public release Tuesday afternoon. "We cannot trust Donald Trump to do either. Therefore we urge our fellow citizens to support an alternative candidate."

The letter comes with just days left until the Iowa caucuses Feb. 1, and as several evangelical leaders have given their support to Trump. Liberty University President Jerry Falwell Jr., son of the late televangelist Jerry Falwell, endorsed Trump on Tuesday, and First Baptist Dallas pastor Robert Jeffress said Saturday that while he cannot officially endorse a candidate, he is "absolutely convinced that Donald Trump would make a great president." Former Republican vice presidential candidate Sarah Palin, who is popular among evangelicals, has also endorsed Trump.

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The 10 signees are all women and include Marjorie Dannenfelser of the Susan B. Anthony List, Beverly LaHaye and Penny Nance of Concerned Women for America, and Jenifer Bowen and Kendra Burger of Iowa Right to Life.

Dannenfelser said in an interview that she is surprised that prominent religious leaders would endorse Trump without getting public assurances of his opposition to abortion and without publicly denouncing comments he has made about women. She accused these religious men of recklessly suspending their disbelief.

"That's not leadership," she said.

Until this week, Trump has largely escaped public questions about abortion on the campaign trail, even as other Republican candidates have found themselves ensnared in nitty-gritty position-taking on abortion issues, as antiabortion activists push them to prove just how much they oppose abortion. This is especially true in Iowa, where conservative evangelicals play a major role in the caucuses.

When questions about abortion come up at town halls, Trump often provides this quick and curt answer: "I am pro-life." He then moves on to other questions. Once, when a questioner pushed harder on the issue, asking whether Trump wants to overturn the landmark Roe v. Wade Supreme Court decision, the candidate simply said that getting enough Supreme Court justices to agree to that would be a challenge.

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On Monday, super PACs supporting the presidential bid of Sen. Ted Cruz (R-Tex.) released an attack ad featuring a 1999 interview in which Trump declared himself "very pro-choice in every respect."

Trump responded to the ad during an interview on MSNBC's "Morning Joe" on Tuesday, saying: "First of all, I am pro-life, and everyone understands that. I'm pro-life." He then shifted to defending himself against a different attack.

In an op-ed published on the Washington Examiner's website on Jan. 23, Trump wrote that his views on abortion were changed by a "personal experience that brought the precious gift of life into perspective for me." Trump wrote that he now opposes abortion except in cases of rape, incest or if the mother's life is in danger. He also wrote that giving government funding to abortion providers is "an insult to people of conscience at the least and an affront to good governance at best."

The letter from activists does not mention the 1999 interview, but it does point out that Trump's sister is Judge Maryanne Trump Barry, who struck down the partial-birth abortion ban in New Jersey, and that he has suggested making former senator Scott Brown, who is pro-choice, his vice president. And it condemns comments Trump has made about others, especially women.

"He has impugned the dignity of women, most notably Megyn Kelly, he mocked and bullied Carly Fiorina, and has through the years made disparaging public comments to and about many women," the letter states. "Further, Mr. Trump has profited from the exploitation of women in his Atlantic City casino hotel which boasted of the first strip club casino in the country."

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When asked why it has taken so long for antiabortion activists to speak out against Trump, Dannenfelser said: "Because he's a great dealmaker, and he's a really nice guy."

Dannenfelser said Trump is the only Republican presidential candidate she has not met with, but she said she was impressed that he agreed to fully defund Planned Parenthood and that he voiced support for the Pain-Capable Unborn Child Protection Act, which would have banned abortion after 20 weeks. Dannenfelser said she doesn't hold Trump's 1999 comments about abortion against him as "there are converts all over the planet."

"He said a couple of things to appease pro-lifers along the way," said Dannenfelser, who has not endorsed anyone. "We ought to hold out for someone better than that."

Here's the full text of the letter:

Dear Iowans,

As pro-life women leaders from Iowa and across the nation, we urge Republican caucus-goers and voters to support anyone but Donald Trump. On the issue of defending unborn children and protecting women from the violence of abortion, Mr. Trump cannot be trusted and there is, thankfully, an abundance of alternative candidates with proven records of pro-life leadership whom pro-life voters can support. We have come to this conclusion after having listened patiently to numerous debates and news reports, but most importantly to Donald Trump’s own words.

The next president will be responsible for as many as four nominations to the Supreme Court. Mr. Trump has given us only one indication about the type of judges he would appoint, and it does not bode well for those who would like to see the court overturn Roe v. Wade. Mr. Trump has said his sister, Judge Maryanne Trump Barry, who struck down the Partial Birth Abortion Ban in New Jersey, would be a “phenomenal” choice for the court. Earlier this month, Mr. Trump also said he thought pro-choice Senator Scott Brown would make a “very good” Vice President. If one truly believes, as we do, that abortion is the taking of an innocent human life and is committed to the pro-life priorities of ending abortion after five months, and defunding the nation’s largest abortion business, Planned Parenthood, it would be a disaster to have a vice president who disagrees.

Moreover, as women, we are disgusted by Mr. Trump’s treatment of individuals, women, in particular. He has impugned the dignity of women, most notably Megyn Kelly, he mocked and bullied Carly Fiorina, and has through the years made disparaging public comments to and about many women. Further, Mr. Trump has profited from the exploitation of women in his Atlantic City casino hotel which boasted of the first strip club casino in the country.

America will only be a great nation when we have leaders of strong character who will defend both unborn children and the dignity of women. We cannot trust Donald Trump to do either. Therefore we urge our fellow citizens to support an alternative candidate.

Jenifer Bowen, Executive Director, Iowa Right to Life
Denise Bubeck, Member and Iowa Volunteer, Concerned Women for America
Kendra Burger, Director of Educational Outreach, Iowa Right to Life
Marjorie Dannenfelser, President, Susan B. Anthony List
Christine Hurley, Iowa Pro-life Activist
Beverly LaHaye, Founder and Chairman, Concerned Women for America
Marilyn Musgrave, Fmr. Congresswoman, VP of Government Affairs, Susan B. Anthony List
Penny Nance, President and CEO, Concerned Women for America
Star Parker, Founder and President, Urbancure
Luana Stoltenberg, Iowa Leader, Operation Outcry