"There has never been a president taking his first worldwide trip being dogged by scandal like this", said Larry Sabato, head of the University of Virginia Center for Politics.
Mr Trump benefits by bringing about a more "fair" deal; he has claimed several times that North Atlantic Treaty Organisation is unfair to the U.S. because of the amount of contributions and support provided by the United States compared to countries like Germany.
Robert Satloff is head of the Washington Institute for Near East Policy.
The agreement, between the U.S. under former president Barack Obama, five other world powers, and Tehran, was viewed with suspicion by Riyadh.
"We are witnessing now a change in the tone, change in policy" from Trump, he said.
The idea of an Arab Nato is not new. "Trump wants to undo all that". Mr. President, you will discover that Riyadh is a loyal and independent ally and is the only one who knows all the keys to wisely and moderately solving [the crises in the region]. During the 2016 election campaign, Trump made critical comments about Muslims.
In Israel, Trump will meet with Israel Prime Minister Benjamin Netanyahu, looking to smooth over fresh tensions.
"Welcome to the White House overseas", said Ari Fleischer, President George W. Bush's former press secretary.
In Brussels, the USA leader will meet with counterparts from North Atlantic Treaty Organisation. He says "expectations are low".
Trump declared Thursday that he's the subject of the "greatest witch hunt" in political history after former FBI Director Robert Mueller was named special counsel to oversee the investigation into the Trump team's ties to Russian Federation.
Meanwhile, the news report highlighted the drawing up of tight security plans to host the leaders. Trump has called it "an ideology that uses a perverted interpretation of religion to justify crimes against all humanity".
"He'll talk about what unites us in uplifting terms, but he'll also be very blunt in talking about the need to confront extremism and the fact that many in the Muslim world have not only not done enough, they've actively abetted this extremism", the senior administration official said. They anxious about Obama's attempts to improve relations with Iran, a country they blame for much of the trouble in the Middle East.
"The president also looks forward to participate in a Twitter forum" in Saudi Arabia, according to his national security advisor.
Donald Trump's visit to Saudi Arabia will reinforce the "strategic partnership" between Saudi Arabia and the USA while boosting their joint fight against the Islamic State of Iraq and the Levant (ISIL) group, the kingdom's foreign minister has said.
Trump leaves Friday on his ambitious nine-day jaunt. Riyadh is the first stop of his foreign tour. "He will visit the Church of the Holy Sepulcher and say a prayer at the Western Wall", McMaster said.
Turki Aldakhil, who runs the Saudi-owned Al-Arabiya news channel, wrote that Trump's visit restores "what Obama ruined".
VOA White House Correspondent Peter Heinlein reported this story.
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