President Donald Trump said Friday morning on Twitter that he's firmly behind anti-abortion advocates who gathered in Washington, D.C. to participate in an annual high-profile rally and march.

'The #MarchForLife is so important. To all of you marching --- you have my full support!' the president tweeted.

Minutes later he note in a second tweet that Vice President Mike Pence will appear in person to address the crowd, declaring that marchers have 'our' support.

Trump will not appear at the event, but Pence's participation will make him the highest-ranking U.S. official to speak there in the march's 44 years.

And Kellyanne Conway lashed out at the pro-abortion movement on Friday as she prepared to deliver her own speech alongside Pence.

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Speaking in person: Vice-president Pence became the first holder of his office ever to address the March for Life

On stage: Mike Pence gained an enthusiastic reception as he became the first vice-president to speak at the March for Life

Speaker: Karen Pence, the vice-president's wife, also addressed the March for Life

President Donald Trump wrote Friday on Twitter that he and Vice President Mike Pence fully support the annual 'March for Life' anti-abortion event convening on the National Mall

Trump said he is firmly behind the marchers; he spent most of his career as a pro-choice centrist but embraced the pro-life movement during his run for the White House

Anti-abortion forces advocate for adoption as an alternative to pregnancy termination

Crowds: The 44th annual March for Life was held close to the Washington Monument at a time when the anti-abortion movement has political momentum in its favor

Trump's senior counselor Kellyanne Conway said Friday morning that America should be 'a culture of life' as she prepared to speak to the nation's largest annual anti-abortion march

'I believe in the sanctity of life. I think that if we can promote and protect life from conception to natural death, it says a lot about our country,' Conway said on the 'Fox & Friends' program from the White House press briefing room.

'I think it's no mistake that in our own Declaration of Independence, life was the very first right that was mentioned. And it was precious then. It remains precious now.'

For the first time in years, abortion opponents will have all the political momentum when they hold their rally on the National Mall.

The March for Life is held each year in Washington to mark the anniversary of the 1973 Supreme Court decision legalizing abortion.

Organizers told the National Park Service in their permit application they expect 50,000 participants. Yet Trump insisted on the eve of the rally that the crowd would be far larger, saying 'a lot of people are gonna be showing up.'

'You know, the press never gives them the credit that they deserve,' Trump told Republicans gathered in Philadelphia. 'They'll have 300, 400, 500, 600 thousand people. You won't even read about it. When other people show up, you read big-time about it. Right? So, it's not fair, but nothing fair about the media.'

The March for Life draws religious and secular opponents to abortion each year, on or near the anniversary of the Supreme Court's 'Roe v. Wade' decision

Pence will be the highest-ranking U.S. official to ever address the March for Life

One of Trump's first official acts after taking office a week ago was to sign an executive order banning U.S. aid to foreign groups that provide abortions.

Pence met with pro-life advocates Thursday night at his office, later tweeting that he 'told them I look forward to addressing National @March_for_Life on Friday.'

Conway said Trump was an unlikely anti-abortion warrior who wounded Hillary Clinton by exposing her support of 'late-term' abortions.

'It took a Manhattan male billionaire who had been pro-choice for most of his life to deliver the most impassioned defense of life in that October 19 debate in Las Vegas, that I've ever heard,' she said, recalling Trump's condemnation of the 'late-term' procedures.

'I've been working on pro-life messaging for over two decades. It took Donald Trump to call out Hillary Clinton and show who's truly extreme on this issue.'

Conway said she hopes the media – which Trump calls the 'dishonest' press – will cover the March for Life with the same zeal it covered the Women's March last weekend

Marchers hear speeches at every March for Life; this year the presenters will include Conway and Pence

Trump delivered a stinging indictment of 'partial-birth' late-term abortions when he debated Hillary Clinton last October in Las Vegas, saying 'it's not okay with me'

In that debate, Trump declared Clinton's position was that ' in the ninth month, you can take the baby and rip the baby out of the womb of the mother just prior to the birth of the baby.'

'Now, you can say that that's okay and Hillary can say that that's okay. But it's not okay with me. ... Honestly, nobody has business doing what I just said, doing that, as late as one or two or three or four days prior to birth. Nobody has that.'

Conway listed a litany of abortion procedures on Friday morning that have enraged pro-lifers, saying Americans should prefer 'a culture of life.'

'We have to stop this culture that just looks the other way: partial birth abortions, sex selection abortions,' she said.

'I can basically go get a pregnancy test and then go get a sex test and schedule my abortion. That's not America's foundation – taxpayer-funded abortion.'

'And of course fetal-pain abortion,' Conway added, 'where nonpartisan, non-political scientists have said an unborn baby can feel pain at 20 weeks, basically the halfway point.'

In Congress, Republican majorities in both chambers are vowing to end federal funding for Planned Parenthood, which provided more than a third of the nation's abortions in 2014. They also hope to ban most abortions after 20 weeks of pregnancy. Trump has pledged to sign both measures if they reach his desk.

Less than a year ago, with Barack Obama's second term winding down, things were markedly different.

Abortion foes held a 'die-in' demonstration on Pennsylvania Avenue near the White House on Friday

KELLYANNE ON ABORTION President Donald Trump's chief counselor Kellyanne Conway spoke to 'Fox & Friends' on Friday about her opposition to abortion: 'I believe in the sanctity of life. I think that if we can promote and protect life from conception to natural death, it says a lot about our country. I think it's no mistake that in our own Declaration of Independence, life was the very first right that was mentioned. And it was precious then. It remains precious now. 'We have to stop this culture that just looks the other way: partial birth abortions, sex selection abortions. I can basically go get a pregnancy test and then go get a sex test and schedule my abortion. That's not America's foundation – taxpayer-funded abortion. And of course fetal-pain abortion, where nonpartisan, non-political scientists have said an unborn baby can feel pain at 20 weeks, basically the halfway point. 'And we just have to look at this as a culture of life. Many presidents and vice-presidents have said they were pro-life. They were. But to have Vice President Mike Pence go out on that mall today, in just a few short hours, and address those who are coming around from the country and indeed the world, to bond together to protect the culture of like, is truly remarkable and historic. And I think it's a big day for Vice President Pence. I hope that Fox will cover it.' Conway noted that Hillary Clinton said during the presidential campaign that she is in favor of supporting women's right to 'late-term abortions': 'Yes she is, and Donald Trump called her out on that. I mean, it took a Manhattan male billionaire who had been pro-choice for most of his life to deliver the most impassioned defense of life in that October 19 debate in Las Vegas, that I've ever heard. 'I've been working on pro-life messaging for over two decades. It took Donald Trump to call out Hillary Clinton and show who's truly extreme on this issue.' Advertisement

Trump took his first anti-abortion action this week, signing an executive order banning federal funding of abortions overseas

The Supreme Court struck down Texas' strict regulations on abortion clinics as interfering with a woman's constitutional right to terminate a pregnancy. And with polls at the time suggesting Hillary Clinton would likely defeat Trump, abortion opponents worried about an era of liberal majorities on the court.

'The horizon looked bleak for the pro-life movement,' said Jeanne Mancini, president of the March for Life.

Mancini suggested that many voters chose Trump largely because he pledged to appoint a Supreme Court justice who shared their views on abortion, even if they disagreed with him on other issues.

'I don't identify as a Republican or a Democrat but I do vote pro-life,' Mancini said.

Abortion opponents also were heartened by a recent study that found the number of abortions in the United States dropped under 1 million in 2014, the lowest total in 40 years. The report by the Guttmacher Institute, which supports abortion rights, credited increased access to birth control but also a surge in abortion restrictions in many states.

Pro-life advocates point to cases like that of Francesca Bradley-Curran, a baby born just two days after the 24-week abortion limit. Francesca weighed less than 2 pounds and her feet were barely wider than pennies

Sister marches have sprung up around the United States, including this rally last week in San Francisco, one of the most liberal locales in America

Americans remain deeply divided on abortion.

The latest Gallup survey, released last spring, found that 47 percent of Americans described themselves as pro-choice and 46 percent as pro-life. It also found that 79 percent believed abortion should be legal in either some or all circumstances.

Ilyse Hogue, president of NARAL Pro-Choice America, said that poll shows why abortion-rights supporters shouldn't despair. She also said Republicans were taking actions that would result in more illegal abortions and deaths of pregnant women.

'The vast majority of Americans support Roe v. Wade and support the legal right to abortion,' Hogue said.

Friday's march comes less than a week after one of the largest mass demonstrations in the city's history, the Women's March on Washington, which drew more than half a million people opposed to Trump on issues including abortion.

Although the landmark Supreme Court decision was Jan. 22, 1973, organizers of the march noted on their website that Trump was sworn in Jan. 20 and the National Park Service assigned Jan. 27 as the next available date for their event.

Mancini said she had planned to participate in the women's march until organizers dropped an anti-abortion group as an official partner. She said its failure to embrace different views on abortion was a missed opportunity.