Donald Trump's maiden international trip, a five-stop marathon across the Middle East and Europe, has long loomed as a crucial first test abroad for the chaos-courting president.
With the eyes of the world upon him, the president will embark on his big trip carrying the baggage of dire troubles at home.
As he tries to calm allies worried about his "America First" message, he will be followed by fallout from his firing of FBI chief James Comey and the appointment of a special counsel to probe the president's campaign ties with Russia.
US allies have also been rattled by his warnings about pulling back from the world.
He is tasked with urging a united front against terror by appealing to some of the same corners of the Muslim world he has tried to keep out of the US with his travel ban.
Last week, he added new layers of complication by disclosing classified intelligence to a long-time adversary, Russia.
The White House once hoped the trip, wrapped in the pomp and circumstance of diplomatic protocol, could offer a chance of a reset after a tumultuous first four months in office.
The agenda is laden with religious symbolism - he will visit the birthplace of Islam, the Jewish homeland and the Vatican.
Officials say the message is "unity", but each stop comes with high stakes.
:: In Saudi Arabia, the president - whose campaign was marked by heated anti-Muslim rhetoric and whose administration has tried to enact a travel ban from several Muslim-majority countries - will deliver a speech to the Islamic world meant to be a clear contrast with the vision Barack Obama laid out in his first trip to the region.
:: In Israel, he will meet prime minister Benjamin Netanyahu, looking to smooth over fresh tensions. Israel was in uproar earlier this week after US officials confirmed Mr Trump shared highly classified intelligence about the Islamic State group with senior Russian officials at the White House. The information, about an IS threat related to the use of laptops on aircraft, came from Israel and there were concerns a valuable Israeli asset could be in danger, a US official said.
National Security Adviser HR McMaster added to the alarm by refusing to declare the Western Wall a part of Israel. US policy holds that ownership of the holiest site where Jews can pray, as with the rest of Jerusalem, is subject to Israeli-Palestinian negotiation.
:: In Rome, the president will call on Pope Francis, the popular, liberal-minded pontiff. Mr Trump denounced Francis during the campaign, calling him "disgraceful" for questioning his faith.
:: In Brussels, he will attend a meeting of Nato, which Mr Trump has repeatedly mused about abandoning because member states were not paying their "fair share". He has recently shifted to reassure wary allies that he remains committed to the pact.
:: In Sicily, the president will meet the other leaders of the G7, a gathering of Western economic powers. Key parts of the group are unsettled by Mr Trump's unpredictability and his willingness to cheer nationalist sentiment.
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