Donald Trump's daughter Ivanka will discuss efforts to combat human trafficking at the Vatican when the President visits for a meeting with Pope Francis tomorrow.

Ivanka Trump will meet with the Community of Sant'Egidio, a modernising movement in the Catholic Church which emphasises the lay role in Catholicism and has grown considerably since the Second Vatican Council (1962-65).

Ivanka is expected to meet several female victims of human trafficking during the session with Sant'Egidio, and discuss ways in which the US government and the Catholic Church may be able to collaborate.

'Ivanka's meetings in Rome are part of the administration's ongoing commitment to combating human trafficking both domestically and abroad,' a White House official said ahead of the trip.

Founded in 1968 by the Italian layman Andrea Riccardi, an historian and former minister in the Italian government, Sant'Egidio emphasises service to the poor, conflict resolution, and ecumenical and inter-faith dialogue, Crux reported.

The group has also long been involved in campaigns against human trafficking, often working with the US Embassy to the Holy See.

Pope Francis is said to favour the group, and at one of his first Angelus addresses from the window of the papal apartment, he spotted a Sant'Egidio banner in the crowd and said, 'Those people from Sant'Egidio are great!'

Ivanka Trump is taking part throughout Trump's nine-day, first overseas trip.

In Saudi Arabia, she participated in a round-table discussion with Saudi women about women's economic issues.

In Jerusalem, she joined her father at the Western Wall, praying at the women's section.

Ivanka, who is the wife of Trump's senior adviser and Middle East point-man Jared Kushner, withdrew from running her clothing brand and from an executive role at the Trump Organisation before joining her father's administration as an unpaid adviser.

Trump's meeting with the Pope, and his daughter's meeting with Sant'Egidio, come days after the White House announced that Callista Gingrich, the wife of former House Speaker Newt Gingrich, will be nominated as the next US Ambassador to the Holy See.

Gingrich will not be part of the US delegation for this trip, as she still has to be confirmed by the Senate.