US President Donald Trump has arrived in Saudi Arabia on his first foreign trip since becoming president.
His eight-day trip will also take in Israel, the Palestinian territories, Brussels, the Vatican, and Sicily.
It comes as Mr Trump faces uproar at home following his sacking of FBI director James Comey.
He has strongly criticised the decision to appoint a special counsel to oversee an inquiry into alleged Russian influence on the US election.
The trip takes in the capitals of the three major monotheistic religions - Islam, Judaism and Christianity.
Hours before Mr Trump's arrival, Saudi air defence units said they had brought down a rocket south of the capital, Riyadh, that was fired from Yemen by Houthi rebels.
Saudi warplanes are reported to have carried out retaliatory strikes on targets close to the Yemeni capital, Sanaa.
Saudi pride and perception of prejudice - Frank Gardner, BBC Security Correspondent, in Riyadh
President Trump's Saudi royal hosts have pulled out all the stops for this visit. They are lavishing him with an extravagant welcome not shown to his predecessor, Barack Obama, whom they felt was soft on their rival, Iran.
Many Saudis are immensely proud that, despite his mounting troubles at home, the US president has chosen their country as the first stop on his inaugural overseas tour. But pressed further, a lot of ordinary Saudis will voice their dislike of US policies in the region and their conviction that the US, and by extension the West, is intrinsically anti-Islamic.
On Sunday President Trump will try to address these concerns in a speech to more than 40 leaders of Muslim nations in which he will call for a united stand against extremism and intolerance.
Some have already commentated that Donald Trump is an unusual choice to deliver such a message but for now, Saudi officials are giving him the benefit of the doubt.
Riyadh - Saturday-Sunday 20-21 May
Mr Trump will attend the Arab Islamic American Summit in Riyadh and speak about his "hopes of a peaceful vision of Islam", in what aides say will be a speech the president hopes will resonate worldwide and express "a common vision of peace, progress and prosperity".
Mr Trump caused controversy during his campaign by calling for Muslims to be temporarily banned from entering the US over security concerns. Legislation aimed at restricting travel from several Muslim-majority countries remains tied up in the US courts.
The summit agenda is expected to focus on combating Islamist militants and the growing regional influence of Iran.
Mr Trump has been a fierce critic of the Iran deal which eased sanctions in return for a curb on its nuclear activities.
One leader who will not be attending the summit will be Sudan's President Omar al-Bashir. President Bashir is wanted by the International Criminal Court on war crimes charges and the US was reported to be unhappy about his planned attendance.
Unlike his predecessor, Barack Obama, Mr Trump is not expected to highlight human rights during his trip.
And aside from the formal diplomacy, US country music star Toby Keith will perform a free concert in Riyadh on Saturday alongside Saudi singer Rabeh Sager.
Saudi Arabia, which enforces a strict interpretation of Islam including a total ban on alcohol, is perhaps an unusual venue for Keith - whose hits include I Love This Bar, Whiskey Girl, and Drunk Americans.
Saturday's concert is open only to men aged over 21, who are required to dress in traditional Saudi tunics.
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.