Billionaire President Donald Trump heads to the Vatican on Wednesday to meet man-of-the-poor Pope Francis, with all eyes on whether they will end their sparring to find common ground.
The two leaders have been at odds over issues from migration to climate change, staking out starkly opposing positions through the media, most notably in 2016 while Trump was campaigning for the US presidency.
But there is a potential for reconciliation: Back in 2013, noting the pontiff's first Christmas as head of the Catholic Church, Trump tweeted that "the new pope is a humble man, very much like me, which probably explains why I like him so much!"
And Francis promised this month that he "won't judge" the former TV personality before hearing him out.
Security will be tight in the world's smallest state, with Swiss Guards joined by anti-terrorism police and sniffer dogs in the wake of the suicide attack at a concert in Manchester, Britain, on Monday claimed by the ISIS group.
During his campaign, Trump evoked the spectre of an IS attack on the Vatican, saying that "if and when" it happens "the pope would have only wished and prayed that Donald Trump would have been president".
Trump's visit to the Vatican is part of his first trip abroad as president, and follows an initial leg in Saudi Arabia and a visit to Israel and the Palestinian territories.
"No president has ever visited the homelands and holy sites of the Jewish, Christian, and Muslims faiths all on one trip," said US National Security Advisor HR McMaster, describing it as a "truly historic" visit.
"He will bring a message of tolerance and of hope to billions."
With his poll numbers at a record low for a new president, Trump may be hoping to boost his popularity by rubbing shoulders with the man who made the cover of Time and Rolling Stone.
At their meeting in the papal library at 0630 GMT, the leaders are expected to discuss issues such as efforts to promote world peace, support for religious freedom and the fight against abortion.
'Play well with voters'
Trump may have sparked tensions with his attempts at a travel ban targeting several Muslim-majority nations, but on Sunday he softened his tone on Islam, rejecting the idea of a battle between religions, a sentiment the pope shares.
Elected in November last year, Trump has already axed rules protecting tax-funded financing of family planning clinics that offer abortions, and has filled an empty spot on the Supreme Court with an anti-abortion justice.
He may also win points thanks to his daughter and high-profile adviser Ivanka Trump, who has made a commitment to fighting human trafficking and will meet victims in Rome after her papal introduction.
Trump's stance on these issues "violates the sanctity of life that people of all faiths and none hold so dear," said Maya Foa, director of the British judicial rights group Reprieve.
And having vowed to make persecuted Christians in the Middle East a foreign policy priority, Trump may be asked by Francis to divert some US humanitarian spending to churches in Iraq and Syria, Vatican expert John L. Allen Jr. said.
If he agreed, it would be "a rare bit of positive news for Trump -- one that should also play well with the religious voters" who elected him, he wrote on Cruxnow.com.
The elephant in the room will be the president's planned border wall with Mexico. The Argentine pope has condemned the idea of using walls to keep out foreigners and slammed those who do as "not Christian".
Trump, who grew up in a Presbyterian family but is not a regular churchgoer, said the accusation was "disgraceful".
And while the pontiff is an ardent supporter of efforts to combat climate change, Trump has pledged to pull the United States out of the COP21 Paris Agreement on reducing greenhouse gas emissions.
The president, who will head to Brussels later Wednesday before returning to Italy for a G7 meeting, did not initially plan to meet the pope.
When the unexpected, last-minute request came, the Vatican squeezed him into an early slot.
Holy See sources said the president would have to enter the papal palace via a side door because the weekly Wednesday mass in Saint Peter's Square takes priority.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)