Pope Leo on Saturday urged people in South America to bridge divides between their countries as he led an event on the Uruguay-Argentina border with tens of thousands on his 12-day trip across a region facing sharp political divisions.

Leo, on an ambitious three-country tour through November 17, travelled some 378 km (235 miles) on Saturday from Montevideo to Paysandu, a riverside economic hub in Uruguay's northwest, where crowds waited to see him outside overnight in heavy rain that eased off shortly before his arrival. He is the first pope to visit the city.

The 71-year-old pontiff, who is making one of the most intense foreign trips of a Catholic leader in decades less than a month after undergoing lung cancer surgery, urged people in Latin America to act with "justice, honesty and faithfulness" towards one another.

Leo, the first US-born pope, is visiting Uruguay until Sunday on the first stop of a tour that will also take him to Argentina and Peru. The Vatican has described the trip as a "homecoming" for Leo, who served as a missionary in Peru for decades and became a Peruvian citizen.

The pope, who has forcefully decried the direction of global leadership in recent months, is expected to address a range of issues facing the continent on the tour, including environmental destruction, arms trafficking and regional political instability.

In his first address of the trip, given to Uruguay's government on Friday afternoon, he urged South American countries to tackle regional issues together and set an example for international cooperation.

Leo will return to Montevideo on Saturday afternoon for several events, including a night-time prayer vigil expected to draw some 60,000 young people.

On Sunday afternoon the pope heads to Argentina, where he will meet and give a speech to President Javier Milei, a libertarian seen as a close ally of US President Donald Trump, who lambasted Leo earlier this year after the pope criticized the Iran war.