President Donald Trump and first lady Melania Trump board Air Force One on Saturday, May, 27, 2017, at Naval Air Station Sigonella in Italy. They were headed back to the United States after a nine-day trip to the Middle East and Europe. Evan Vucci/AP

President Trump greets people on May 27, after speaking to US troops at Naval Air Station Sigonella. Evan Vucci/AP

President Trump addresses US troops and their families on May 27, at the Sigonella Naval Air Station. Luca Bruno/AP

President Trump and first lady Melania Trump arrive on May 27, to address US military personnel and families at Naval Air Station Sigonella. MANDEL NGAN/AFP/Getty Images

Leaders of the G-7 and some African nations pose for a photo on May 27, on the second day of the G-7 summit in Taormina, Italy. TIZIANA FABI/AFP/Getty Images

President Trump gestures on May 27, during a G-7 session. Christian Minelli/NurPhoto/Getty Images

President Donald Trump and his wife, Melania, arrive for a concert of the La Scala Philharmonic Orchestra while in Taormina, Italy, on Friday, May 26. The Trumps are in Italy for a two-day G-7 summit. MANDEL NGAN/AFP/Getty Images

Trump and other leaders pose for a group photo at the G-7 summit on May 26. From left are European Council President Donald Tusk, Canadian Prime Minister Justin Trudeau, German Chancellor Angela Merkel, Trump, Italian Prime Minister Paolo Gentiloni, French President Emmanuel Macron, Japanese Prime Minister Shinzo Abe, British Prime Minister Theresa May and European Commission President Jean-Claude Juncker. Andrew Medichini/AP

Trump and Trudeau walk together after the group photo. Evan Vucci/AP

G-7 leaders congregate during a walking tour on May 26. Evan Vucci/AP

Trump embraces new French President Emmanuel Macron on May 26. Andrew Medichini/AP

The leaders watch a French air squadron. JONATHAN ERNST/AFP/Getty Images

Melania Trump arrives at the City Hall in Catania, Italy, on May 26. She was wearing a $51,500 Dolce & Gabbana jacket as she met with other spouses of G-7 leaders. Domenico Stinellis/AP

Trump shakes hands with Macron in Brussels, Belgium, on Thursday, May 25. They were attending a NATO summit as the alliance officially opened a new $1 billion headquarters. Jasper Juinen/Bloomberg/Getty Images

Trump stands with other world leaders during a NATO photo shoot on May 25. Stefan Rousseau/Pool/Getty Images

Trump speaks with British Prime Minister Theresa May during a working dinner at NATO headquarters. Matt Dunham/Pool/AP

Trump stands next to German Chancellor Angela Merkel at the NATO summit. Kay Nietfeld/picture-alliance/dpa/AP

Melania Trump visits the Magritte Museum in Brussels with Amelie Derbaudrenghien, partner of Belgian Prime Minister Charles Michel. ERIC LALMAND/AFP/Getty Images

A girl takes a selfie with Melania Trump at a children's hospital in Brussels on May 25. Virginia Mayo/AP

Trump meets with Macron in Brussels. Peter Dejong/AP

Trump walks with European Council President Donald Tusk, center, and European Commission President Jean-Claude Juncker, right, after they met at the European Council in Brussels on May 25. ROBERT GHEMENT/EPA/REX/Shutterstock

Trump, third from right, attends a meeting with leaders at the European Council. Stephanie Lecocq/AP

Trump speaks with King Philippe of Belgium as Queen Mathilde and Melania Trump chat during a reception at the Royal Palace in Brussels on Wednesday, May 24. BENOIT DOPPAGNE/AFP/Getty Images

Tusk talks to Trump as he welcomes him in Brussels. EMMANUEL DUNAND/AFP/Getty Images

Trump stands with Belgian Prime Minister Charles Michel while the national anthem is played during Trump's arrival in Belgium on May 24. Geert Vanden Wijngaert/AP

Protesters in Brussels demonstrate with effigies of Trump and Michel on May 24. ERIC FEFERBERG/AFP/Getty Images

Trump shakes hands with Italian President Sergio Mattarella in Rome on May 24. Evan Vucci/AP

Pope Francis stands with Trump and his family during a private audience at the Vatican on May 24. Joining the President, from left, are Trump's son-in-law, White House senior adviser Jared Kushner; Trump's daughter and adviser Ivanka Trump; and first lady Melania Trump. ALESSANDRA TARANTINO/AFP/Getty Images

Trump and the Pope exchange gifts. Trump presented the Pope with a first-edition set of Martin Luther King's writings. The Pope gave Trump an olive-tree medal that the Pope said symbolizes peace. Vatican Pool/Getty Images

Trump and his wife look at the ceilings of the Sistine Chapel. L'Osservatore Romano/Pool Photo via AP

Trump speaks to reporters in Rome during a meeting with Italian Prime Minister Paolo Gentiloni, right, on May 24. Evan Vucci/AP

The first lady visits a pediatric hospital in Vatican City on May 24. Franco Origlia/Getty Images

Melania Trump arrives at the Vatican on May 24. With Vatican protocol in mind, she wore a black veil and long-sleeved black dress draped down to her calf. Ivanka Trump wore a similar outfit with a larger veil. VINCENZO PINTO/AFP/Getty Images

President Trump and Israeli Prime Minister Benjamin Netanyahu wave at the Israel Museum in Jerusalem on Tuesday, May 23. Trump gave a speech there, reaffirming his country's commitment to Israel while also holding up Judaism's historical ties to the United States. Sebastian Scheiner/AP

People take pictures of the message Trump wrote at Yad Vashem, the Holocaust memorial in Jerusalem, on May 23. GALI TIBBON/AFP/Getty Images

With the help of US Marines, Trump and his wife lay a wreath at Yad Vashem. MANDEL NGAN/AFP/Getty Images

Trump meets with Mahmoud Abbas, the President of the Palestinian Authority, on May 23. Trump met with Israeli leaders the day before and said he believes both sides "are ready to reach for peace." Evan Vucci/AP

A Palestinian security official takes position before the arrival of Trump's convoy in Bethlehem, West Bank. ALAA BADARNEH/EPA

Israeli and American activists hold signs Monday, May 22, during an anti-Trump protest next to the US embassy in Tel Aviv, Israel. Oded Balilty/AP

Melania Trump and Israeli first lady Sara Netanyahu speak to children during their visit to the Hadassah hospital in Jerusalem on May 22. SEBASTIAN SCHEINER/POOL/EPA

Trump talks to reporters as he meets with Israeli Prime Minister Benjamin Netanyahu on May 22. Trump sought to rebut claims that he damaged Israeli intelligence capabilities by revealing highly classified information to Russian operatives earlier this month. "Just so you understand, I never mentioned the word or the name Israel," Trump told reporters as he began the second leg of his first foreign tour. Evan Vucci/AP

Trump touches the Western Wall, Judaism's holiest prayer site, while in Jerusalem on May 22. Trump became the first sitting US president to visit the wall. RONEN ZVULUN/POOL/EPA

Trump stands in the Western Wall plaza. To his left, in black, is Shmuel Rabinowitz, the rabbi of the Western Wall. Ronen Zvulun/Pool via AP

First lady Melania Trump, in white, visits the Western Wall. At far left is Ivanka Trump. HEIDI LEVINE/AFP/Getty Images

The President and first lady plant a tree in Jerusalem with Israeli President Reuven Rivlin. Evan Vucci/AP

Trump is welcomed by Netanyahu upon arriving in Tel Aviv on May 22. Trump started his trip with two days in Saudi Arabia. JIM HOLLANDER/EPA

On the way to Tel Aviv, US Secretary of State Rex Tillerson speaks with reporters aboard Air Force One. Evan Vucci/AP

While in Riyadh, Saudi Arabia, Trump attends the inauguration ceremony for the Global Center for Combating Extremist Ideology. Joining him here are Saudi King Salman bin Abdulaziz Al Saud, center, and Egyptian President Abdel Fattah el-Sisi, left. EPA/SAUDI PRESS AGENCY

Trump speaks in Riyadh during the Arab Islamic American Summit on Sunday, May 21. Trump looked to make it clear that the United States is not at war with Islam. "This is not a battle between different faiths, different sects or different civilizations," he said. "This is a battle between barbaric criminals who seek to obliterate human life, and decent people of all religions who seek to protect it. This is a battle between good and evil." MANDEL NGAN/AFP/Getty Images

Trump sits at the summit, which included leaders from 55 Muslim-majority countries. He urged them to do more to eradicate terrorist groups that claim the mantle of Islam. "We can only overcome this evil if the forces of good are united and strong and if everyone in this room does their fair share and fulfills their part of the burden," Trump said. "Muslim-majority countries must take the lead in stamping out radicalization." MANDEL NGAN/AFP/Getty Images

Trump poses with other leaders at the Arab Islamic American Summit. MANDEL NGAN/AFP/Getty Images

Saudi King Salman shakes hands with Trump on May 21. Trump is the first US president to start his first foreign trip in the Middle East. BANDAR ALGALOUD/SAUDI ROYAL COUNCIL/HANDOUT/Anadolu Agency/Getty Images

Trump meets with other heads of state in Riyadh on May 21. BANDAR ALGALOUD/SAUDI ROYAL COUNCIL/Anadolu Agency/Getty Images

Trump speaks with the Crown Prince of Abu Dhabi, Gen. Sheikh Mohammed Bin Zayed Al Nahyan. BANDAR ALGALOUD/SAUDI ROYAL COUNCIL/HANDOUT/Anadolu Agency/Getty Images

First lady Melania Trump chats with children during a visit to the American International School in Riyadh on May 21. GIUSEPPE CACACE/AFP/Getty Images

While in Riyadh, President Trump meets with Bahrain's King Hamad bin Isa Al Khalifa on May 21. Evan Vucci/AP

President Trump and Egyptian President Abdel Fattah el-Sisi share a laugh during a meeting on May 21. El-Sisi complimented Trump on his "unique personality that is capable of doing the impossible." Trump exchanged pleasantries back, praising el-Sisi's shoes. Evan Vucci/AP

Trump is handed a sword during a welcoming ceremony at Riyadh's Murabba Palace on Saturday, May 20. Evan Vucci/AP

Trump sits with members of his staff and Cabinet before a meeting with Saudi King Salman on May 20. Evan Vucci/AP

Trump and King Salman take part in a signing ceremony at the Saudi Royal Court in Riyadh on May 20. The two leaders oversaw the signing of a defense deal worth nearly $110 billion. MANDEL NGAN/AFP/Getty Images

The Trumps look at a display of modern art at the Saudi Royal Court in Riyadh. MANDEL NGAN/AFP/Getty Images

King Salman presents Trump with a gilded necklace and medal, the country's highest honor. The distinction also was bestowed upon Presidents Barack Obama and George W. Bush. MANDEL NGAN/AFP/Getty Images

The first lady chats with Saudi Crown Prince Muhammad bin Nayef at the medal ceremony on May 20. MANDEL NGAN/AFP/Getty Images

Ivanka Trump attends the medal ceremony. Evan Vucci/AP

Trump meets with King Salman after arriving in Riyadh on May 20. Evan Vucci/AP

Soldiers on horseback carry the US and Saudi flags as they escort Trump to the Saudi Royal Court in Riyadh. SAUDI PRESS AGENCY/EPA

Trump is welcomed by King Salman after arriving at the King Khalid International Airport in Riyadh. MANDEL NGAN/AFP/Getty Images

The Trumps take part in the welcome ceremony. MANDEL NGAN/AFP/Getty Images