WASHINGTON - Thousands of marchers braved freezing temperatures in Washington on Wednesday to demand an end to abortion in the United States, with Pope Francis tweeting his support.
The annual March for Life marks the anniversary -- in this case the 41st -- of the US Supreme Court's landmark Roe versus Wade decision that effectively legalized abortion nationwide.
"We're pro-life because we believe in the rights of unborn children," March for Life president Jeanne Monahan told the crowd on the snow-covered National Mall, with the Capitol in the distance.
On Twitter, where he has three million followers in English, Pope Francis sent from the Vatican a message of support to the protesters, including large numbers of Roman Catholics.
"I join the March for Life in Washington with my prayers," said the pontiff, who last year denounced abortion as a symptom of today's "throw-away culture."
"May God help us respect all life, especially the most vulnerable," he added.
US President Barack Obama, who has expressed admiration for some of the pope's messages and is due to meet him in Rome in March, is on the other side of the debate.
In a statement to mark the anniversary, the White House reaffirmed Obama's position that "every woman should be able to make her own choices about her body and her health.
"We reaffirm our steadfast commitment to protecting a woman's access to safe, affordable health care and her constitutional right to privacy, including the right to reproductive freedom," it said.
At the rally on the nearby Mall, speaker after speaker mourned the estimated 56 million fetuses which, they said, have been "brutally slayed" in American abortion clinics over the past four decades.
"Our society and our leaders must stop upholding abortion and start encouraging adoption," said Vicky Hartzler, a Republican congresswoman and Tea Party favorite from Missouri.
"Abortion hurts everyone," she declared.
Fifty-three percent of Americans support a woman's right, in consultation with her doctor, to decide whether or not to undergo an abortion, the principle enshrined by Roe versus Wade, according to a Gallup poll at the end of last year.
Twenty-nine percent want the Supreme Court ruling overturned, however, while 18 percent have no opinion on the matter -- the highest level since Gallup started asking the question in 1989.
Another poll, by YouGov.com for the Huffington Post website, found 47 percent supporting Roe versus Wade, 33 percent against and 20 percent "not sure."
But the anti-abortion movement -- underpinned by the Catholic church and social conservatives -- remains a political force to be reckoned with, not least with the 2016 presidential election looming.
Last year alone, 22 of the 50 states enacted a total of 70 abortion restrictions -- the greatest number in any year besides 2011, according to the Guttmacher Institute, a specialist think tank.
The issue, meanwhile. returned to the Supreme Court last week when its nine justices heard arguments over a Massachusetts law creating a buffer zone around abortion clinics targeted by pro-life activists.
Pro-abortion advocates cancelled plans for a counter-protest in Washington on Wednesday, citing the cold snap that followed a snowstorm Tuesday up and down the northeastern US coast.
On their stoppatriarchy.org website, they lashed out at what they called "a Christian fundamentalist-driven assault ... imperiling abortion, birth control, real sex education and women's lives."
In the pro-life crowd Wednesday, university graduate Kristin Hagelin, 21, attending her first March for Life, said her opposition to abortion took shape "quite recently" after her boyfriend proposed to her and she reflected on married life.
"A lot of people don't realize how horrible abortion is," she told AFP as she handed out "I Am the Pro-Life Generation" placards.
"Even just seeing pictures of what abortion is -- it's tearing a life apart."
From Pittsburgh, 57-year-old electrical engineer Don Kirkwood, a member of the Blue Army of Our Lady of Fatima, marched with a statue of the Virgin Mary, "a role model for all young mothers."
"It seems it's getting worse rather than better," he said when asked how he thought the struggle against abortion was going.
"Even Catholics in Congress and the Senate are not doing what good Catholics should do," he complained.
But Kirkwood, who has attended every March for Life for the past 20 years, added: "What I find encouraging are all the young people here."
© 1994-2014 Agence France-Presse