The United States Conference of Catholic Bishops estimates that tens of thousands of people will take part in a 24-hour prayer vigil for the unborn at the Basilica of the National Shrine of the Immaculate Conception.
The pilgrims will pray for an end to abortion. A Mass will be led by Cardinal Timothy Dolan of New York, chairman of the US bishops' Committee on Pro-Life Activities.
"Each year, the National Prayer Vigil for Life is a joyful, if sober, event, with thousands of young people from around the country. Led by our bishops, we are working to end abortion through prayer, education, advocacy, and acts of mercy," said Deirdre McQuade, assistant director for pro-life communications.
The prayer vigil, hold annually ahead of the March for Life, comes just days after Donald Trump issued an executive order banning NGOs that perform abortion from receiving US funding.
On the campaign trail, Trump said that he supports an abortion ban except in incidents of "rape, incest and the life of the mother."
The Republican-majority Congress has also indicated that it intends to withdraw federal funding from Planned Parenthood, who provide reproductive health services in the US.