Simultaneously, Saudi Arabia is in a broad-based push for economic reform, and as part of that effort signed a flurry of deals with private US companies worth tens of billions of dollars. He repeatedly demanded that the Saudis compensate the United States for its long-standing alliance.
The U.S. president and the Saudi king, or their designees, will meet at least once a year to discuss new strategies, alternating between the two countries, the White House also said.
Tillerson and Commerce Secretary Wilbur Ross raised swords and linked arms with Saudis, chanting to the beat of feathered drums, while Chief of Staff Reince Priebus, chief strategist Stephen K. Bannon and National Economic Council director Gary Cohn also laughed and swayed.
Other items are meant to modernise Saudi Arabia's cyber-defence and airborne intelligence-gathering, and secure its borders.
"The package of defence equipment and services supports the long-term security of Saudi Arabia and the entire Gulf region", he told a news conference in Riyadh.
King Salman gave a more favorable welcome to Trump than he had granted previous year to Trump's predecessor, Barack Obama, who was seen in the Arab kingdom as soft on Iran and hesitant on Syria.
President Donald Trump arrived in the Middle East on Saturday, touching down in Saudi Arabia to begin his first trip overseas, a visit aimed at forging stronger alliances to combat terrorism while seeking to push past the series of controversies threatening to engulf his young administration. Then-first lady Laura Bush generally went without covering her head, though she once briefly donned a headscarf that she received as a gift. Saudi Arabia honored President Donald Trump Saturday by bestowing him with their nation's highest honor, the Collar of Abdulaziz Al Saud.
The mood in Riyadh was in sharp contrast to Washington where pressure is building after fresh claims over the Trump team's alleged links to Moscow.
The speech comes as Trump tries to escape the fallout from his May 9 firing of former FBI Director James Comey amid accusations he was trying to stop a federal investigation into his campaign's ties with Russian Federation past year.
Fanning the flames was a New York Times report that Trump had called Comey a "nut job" in a private meeting last week in the Oval Office with Russian Foreign Minister Sergei Lavrov and ambassador Sergei Kislyak.More news: Security experts struggle in search for WannaCry clues
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After talks with senior Saudi officials on Saturday, Trump was to give a speech to dozens of Muslim leaders on Sunday.
The speech has been touted as a major event along the lines of a landmark address to the Islamic world given by his predecessor Barack Obama in Cairo in 2009. Billboards featuring images of Trump and the king dotted the highways of Riyadh, emblazoned with the motto "Together we prevail".
The deals were announced during the Saudi-US CEO Forum 2017 coinciding with the visit of US President Donald Trump.
Mr Trump's eight-day trip will also take in Israel, the Palestinian territories, Brussels, the Vatican, and Sicily.
The avalanche of revelations in the run-up to his departure has eroded Trump's standing at home - where the parallels with Richard Nixon's ill-fated presidency are now being openly drawn. The Washington Post said the probe had reached into the White House to include a Trump adviser, who was not named.
The scandals have revived questions about his ability to strike a presidential tone with his foreign counterparts.
In a litany of tweets, Stone berated Saudi Arabia as "the enemy" and slammed Trump for accepting the Order of Abdulaziz from King Salman bin Abdulaziz.
As Trump arrived, Iranians had just re-elected Hassan Rouhani - one of Obama's partners in the landmark accord aimed at curbing Tehran's nuclear ambitions - for a second four-year-term as president, validating his push for greater freedoms and outreach to the wider world. "We have to get to the bottom of it", Trump said in a March 2016 interview with CNN.
The president will then meet members of North Atlantic Treaty Organisation in Brussels and attend a G7 summit in the picturesque Sicilian town of Taormina overlooking the Mediterranean.