In front of hundreds of world leaders attending the funeral of Pope Francis on Saturday (April 26), Italian Cardinal Giovanni Battista Re  called for care for migrants, an end to wars, and action on global climate change - Francis' favorite political themes.

Re repeated one of the pope's strongest criticisms of U.S. President Donald Trump, with Trump himself present in the crowd, by calling to "build bridges, not walls."

Trump and the pope exchanged criticisms over a decade, mostly related to the pope's plea for compassion for migrants, a group Trump has repeatedly sought to deport.

READ: Hundreds of thousands at funeral for pope 'with an open heart'

Re's sermon, heard by a global audience of millions, contained a strong political message for the national leaders and a strong internal message to the world's Catholic cardinals.

To the about 135 Catholic cardinals who will soon be tasked with entering a secret conclave to choose the next pope, it was also a possible roadmap for how they should start their deliberations.

In spiritual language, the 91-year-old prelate gave a simple message: there is no going back.

Francis, pope since 2013, died on Monday at age 88.

His funeral on Saturday, which also included Ukrainian President Volodymyr Zelenskiy and some 50 other world leaders, was a carefully choreographed affair, with Latin chants, strictly organized seating, and use of ancient Catholic rites.

Re invoked a criticism Francis levied against Trump in 2016, when the real estate mogul was making his first run for president. Trump, the pope said, was "not Christian" because of his views on immigration.

"A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian," said Francis at the time. "This is not in the gospel."

Trump responded then, "For a religious leader to question a person's faith is disgraceful."

More recently, the pope had called Trump's immigration crackdown in his second term a "disgrace."

(Production: Orianna Boselli, Chiara Rodriquez)