The 78-year-old sees himself as the spokesman for democracy in the face of authoritarian regimes, notably China.
Joe Biden and Pope Francis have met three times already.
Vatican City, Holy See: As world leaders flock to Rome for the G20 summit, US President Joe Biden met Pope Francis Friday at the start of a trip aimed at reasserting US international credentials.
Shortly before leaving Washington, the president unveiled an "historic" blueprint for remaking America's economy, but it remains to be seen if he can persuade lawmakers to back it.
After weeks of internal party feuding, and with his personal ratings slumping, Biden had hoped to arrive at twin summits in Europe this week -- the G20 and UN climate talks in Glasgow -- with the deal in hand.
The 78-year-old sees himself as the spokesman for democracy in the face of authoritarian regimes, notably China -- although Xi Jinping, like Russia's Vladimir Putin, is not attending the G20 in person.
The president opened the trip on a more intimate note. After landing overnight, he arrived at the Vatican just before lunch for a meeting with Pope Francis, the head of the world's 1.3 billion Catholics.
The presidential convoy carrying Biden and his wife Jill swept through St Peter's Square before winding its way to the Apostolic Palace, where a line of guards and Vatican dignitaries awaited the US guests.
- First meeting as president -
St Peter's bells chimed just after the Bidens arrived in the Cortile San Damaso.
The US president and his wife, who was wearing a black dress and veil, as is traditional when meeting the pope, were received by Cardinal Pietro Parolin, the Vatican's secretary of state.
Biden and Francis have met three times already, but this was their first tete-a-tete since Biden was elected.
Only the second ever Catholic president, Biden attends mass regularly and is open about his faith.
The White House said it expects the meeting to be "warm", and Biden and the pope share a range of concerns, from poverty to climate change and the coronavirus pandemic.
But the question is whether either leader raises the red-button issue of abortion. Biden supports the right to choose, while Francis, 84, has slammed terminating pregnancies as "murder".
The pontiff has nonetheless distanced himself from a push by conservative US bishops to deny communion to politicians supportive of abortion rights -- which would include Biden.
The meeting will be behind closed doors and the Vatican abruptly cancelled a live camera feed, to protests from journalists.
- Charm offensive -
Biden then crosses the Tiber into the heart of the Eternal City to meet Italian Prime Minister Mario Draghi -- the man, dubbed "Super Mario", tasked with reforming the country after the devastation of Covid-19.
The G20 host is being closely watched in Washington for his plans to set debt-laden and politically fractious Italy back on track.
But while Draghi is feted as the new star of European politics, particularly with the exit of German Chancellor Angela Merkel, Biden appears to have lost some of his shine.
The president is banking his domestic legacy on passing the $1.75 trillion Build Back Better social welfare package, and also hopes it will present the US as a global leader on climate change at the crucial COP26 summit starting on Monday.
He said it includes "the most significant investment to deal with the climate crisis ever" -- 550 billion dollars to cut greenhouse gas emissions.
"America is back in a leadership position on climate in a way that will be broadly welcomed," National Security Advisor Jake Sullivan told reporters on the flight over.
Biden, a veteran foreign policy expert, is determined to distance himself from the unilateralism of ex-president Donald Trump, and will be seeking to soothe ruffled feathers.
He will have some fence-mending to do after a chaotic withdrawal from Afghanistan, which irritated US allies, and a major spat over nuclear-powered submarines.
Biden will meet Friday with French President Macron for the first time since the subs row, in what Sullivan said was expected to be a "constructive and deeply substantial meeting".
Biden and Macron are expected to meet again Saturday alongside Merkel and Britain's Boris Johnson to discuss attempts to get Iran back into negotiations on submitting its nuclear industry to international inspections.