Pope Francis has added 13 new cardinals to the top of the Catholic hierarchy, telling them they must show God's compassion to those who suffer to be faithful to their ministry.

Francis presided over the ceremony on Saturday in St. Peter's Basilica, elevating churchmen who share his pastoral concerns at a time when his pontificate is under fire from conservatives within the College of Cardinals itself.

Among the 13 are 10 cardinals who are under age 80 and therefore eligible to vote in a conclave, increasing the likelihood that a future pope might end up looking an awful lot like the current one. These are churchmen who care for migrants, promote dialogue with Muslims and minister to the faithful in poor, far-flung missionary posts.

With Saturday's consistory, Francis will have named 52% of the voting-age cardinals. Many hail from churches in the developing world that never have had a 'prince' representing them in a sign of Francis' desire to mirror the universal face of the Catholic Church in the church's leadership ranks.

Francis was in many ways preaching to the choir when he urged the new cardinals to both feel and share God's compassion, saying it was an 'essential' part of understanding God's love for the weakest and most marginal.

'If I don't feel it, how can I share it, bear witness to it, bestow it on others?' he asked in his homily. 'So many disloyal actions on the part of ecclesiastics are born of the lack of a sense of having been shown compassion, and by the habit of averting one's gaze, the habit of indifference.'

The consistory comes at a fraught time in Francis' six-year papacy. Opposition is mounting among conservative Catholics who disapprove of his emphasis on the environment, migrants and other issues rather than the doctrinaire focus of his predecessor Pope Benedict XVI.

Yet in a sign of continuity with the past pope, Francis and the new cardinals made a pilgrimage across the Vatican gardens after the ceremony on Saturday evening to call on Benedict, who gave them his blessing, the Vatican said.

Francis has acknowledged criticism in the US church but shown no sign that such conservative outrage is hampering his agenda. After he stacks the College of Cardinals with more like-minded men, he will on Sunday open a three-week meeting on better ministering to the indigenous peoples of the Amazon region.

Right-wing groups backed by a handful of conservative cardinals have come out in force against the Amazon synod's environmental emphasis, saying it amounts to a heretical attempt to create a new 'pagan' religion.

A Canadian priest elevated on Saturday, cardinal Michael Czerny, said he thinks the criticism is coming from a small fringe with vested interests in developing the Amazon and pursuing other priorities incompatible with the pope's vision.

'He's meeting with some loud opposition. I don't think it's so much,' Czerny told The Associated Press ahead of the consistory. 'I think it's loud.'

Czerny is clearly a Francis favorite, someone in whom the pope sees a cardinal he can entrust his most important dossiers. Czerny has worked since 2010 in the Vatican's justice office, where he helped draft Francis' major environmental encyclical. In 2016, Francis made Czerny his personal point-man on migrant issues, and the pectoral cross he sported on Saturday showed he took the mission to heart: It was made of wood from a migrant ship.

A Jesuit like the pope, Czerny went to El Salvador in 1989 after six Jesuit confreres were gunned down at Central American University. For a South American Jesuit like Francis, the killings were an unfathomable assault that laid bare the order's social justice ethos, the same ethos that years later would inform his papacy.

Several other prelates with experience in another of Francis' agenda items – relations with Islam – also received red hats, including the head of the Vatican's interfaith relations office, cardinal Miguel Angel Ayuso Guixot, and Guixot's predecessor in that job, cardinal Michael Fitzgerald.

Long considered one of the church's leading experts on Islam, Fitzgerald was removed as president of the Pontifical Council for Interreligious Dialogue in 2006 and sent off to Egypt as the Vatican's ambassador. His removal came a month before Benedict folded the interfaith relations office into the Vatican's culture ministry, in a move seen as reducing dialogue with Islam in a post-9/11 world.

The Vatican restored the office as its own entity the following year after Benedict enraged the Muslim world with a now-infamous speech equating Islam with violence. Only recently under Francis have Catholic-Muslim relations healed.

Many commentators have seen Francis' decision to make Fitzgerald a cardinal as a righting of a past wrong. Fitzgerald, who is over 80 and unable to vote in a conclave, was diplomatic when asked about the significance that both he and his successor were receiving red hats, saying it showed 'continuity.'

Another new cardinal over the voting age limit was a clear sentimental favorite for Francis: Lithuanian cardinal Sigitas Tamkevicius, a Jesuit who was imprisoned and sent to labor camps for 10 years, some of them in Siberian exile, for his anti-Soviet activities.

Tamkevicius accompanied Francis last year on a visit to site of a KGB prison in Vilnius where he was held, one of the most moving moments of the pope's trip to Lithuania.

'In prison, there were difficult moments, very difficult moments, and the worst was when I was interrogated,' Tamkevicius told journalists at the Vatican this week. 'The interrogation would last for months and months.'

He said he was thankful to God 'for all these years that I have had as priest, as bishop, as archbishop.'

'I ask that he allows me to go on a lot longer so that I can face the challenges of today and always have the faith in my heart,' Tamkevicius said.