Pope Francis on Sunday canonised the first female saint from his native Argentina, an event that brought his former fierce critic, Argentine President Javier Milei, to the Vatican.

Francis led a canonisation Mass in St. Peter's Basilica for Maria Antonia de Paz y Figueroa, better known as "Mama Antula", an 18th century consecrated lay woman who renounced her family's riches to focus on charity and Jesuit spiritual exercises.

Milei had a front row seat for the service, and at the end of it, exchanged a few words with the pope, as they shook hands and hugged. The president is due to have a private audience with Francis on Monday.

The ceremony came as Argentina faces its worst economic crisis in decades, with inflation at more than 200%, and the newly installed Milei in difficulty following parliamentary rejection of a major reform package.

Before he ran for president, Milei, a maverick right-wing libertarian, had insulted Francis in strongly worded comments, but has softened his tone since taking office in December.

The pope "is the most important Argentine in history", Milei told Radio Mitre on Saturday.

In his Argentine radio interview, Milei said he was looking forward to "a very fruitful dialogue" with Francis, and hoped that the 87-year-old pontiff's health would be good enough to face a trip to Argentina.

Francis, a former archbishop of Buenos Aires who has angered some of his compatriots by never visiting his homeland since becoming pope in 2013, has said he may finally make the journey in the second half of this year.

Mama Antula was the daughter of a wealthy landholder and slave owner.

She promoted spiritual exercises, including prayers and meditation, walking thousands of kilometres barefoot and involving the rich and poor in these endeavours, despite the Jesuits being banished at the time from Latin America.

Francis, himself a Jesuit, described her on Friday as a "gift to the Argentine people and also to the entire Church."

Quoting from his past writings, the pope condemned the "radical individualism" that permeates society as a "virus", in words that may jar with Milei's radical free-market instincts.

In his homily on Sunday, he returned to the issue of caring for the poor and outcasts, saying "fear, prejudice and false religiosity" lead people to the "great injustice" of ignoring the plight of the weak.