Donald Trump is on his first foreign trip since becoming US president in January.
He started with Saudi Arabia over the weekend, urging Muslim countries to take the lead in combating radicalisation.
Mr Trump will also visit Israel, the Palestinian territories, Brussels, the Vatican, and Sicily.
So, what's on the agenda during his eight-day tour that takes in the capitals of the three major monotheistic religions - Islam, Judaism and Christianity?
Israel and the West Bank - Monday-Tuesday 22-23 May
On Monday, Mr Trump will fly to Tel Aviv and travel on to Jerusalem where he will meet President Reuven Rivlin.
He is due to visit the Church of the Holy Sepulchre as well as the Western Wall before holding talks with Israeli Prime Minister Benjamin Netanyahu.
Observers will be watching to see if Mr Trump refers to his announcement during the election campaign, that he would break with decades of US policy and move the US embassy from Tel Aviv to Jerusalem.
The status of Jerusalem is one of the most sensitive and complex issues within the Middle East conflict and no country in the world currently has its embassy there.
On Tuesday, Mr Trump will travel to Bethlehem in the West Bank for talks with Palestinian President Mahmoud Abbas. Peace talks with Israel will top the agenda and Mr Trump is expected to express his support for Palestinian "self-determination".
Rome and Brussels - Wednesday 24 May
President Trump will arrive early in Rome and have an audience with Pope Francis.
The two men have appeared at odds on many subjects including climate change and the plight of refugees, but the Pope has said he will give the president an open-minded hearing.
Later, Mr Trump flies to Brussels where he will be greeted by King Philippe of Belgium and Prime Minister Charles Michel.
Brussels - Thursday 25 May
After talks with EU leaders and France's new President Emmanuel Macron, Mr Trump will attend a meeting of Nato leaders.
This will be closely watched after Mr Trump's conflicting pronouncements on the alliance. During his campaign, he called Nato "obsolete", although in April he reversed his stance.
The US leader is expected to repeat his demand that other Nato members increase their contributions.
Sicily - Friday 26 May
The last stop on Mr Trump's tour will be the picturesque Sicilian town of Taormina where he will attend a G7 summit.
Correspondents say the other G7 leaders are eager to hear Mr Trump's thoughts on trade and other issues at first hand.
Mr Trump's national security adviser has said that the president will "press America's economic agenda and call for greater security co-operation".
Find out which foreign leaders President Trump has met or called since taking office, as well as the countries he has mentioned in his tweets.