As he arrived, the president waved from the doorway of Air Force One and then descended the steps, joined by First Lady Melania Trump.
Pakistan Prime Minister Nawaz Sharif will attend the first ever Arab-Islamic-American Summit being held in Riyadh on Sunday, a media report said on Saturday.
Mr Trump will addresses the leaders of Arab and Muslim nations in Saudi Arabia on Sunday.
Trump and King Salman seemed at ease with each other, chatting through an interpreter.
President Trump will also visit Israel, Palestine, Brussels, the Vatican and Sicily during his eight-day-long first foreign trip since becoming president.
Dogged by controversy at home, President Donald Trump opened a nine-day foreign trip on Saturday in Saudi Arabia, looking to shift attention from a spiraling political firestorm over his firing of former FBI Director James Comey last week. Walking with a cane, the king greeted Trump on the tarmac.More news: Ottawa Senators vs. Pittsburgh Penguins - 5/19/17 NHL Pick, Odds, and Prediction
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After a royal banquet, Trump and the king were to have private talks and participate in a signing ceremony for a number of U.S. -Saudi agreements, including a $100 billion deal for Saudi Arabia to buy American arms.
The president was already under attack for firing Comey in the midst of an Federal Bureau of Investigation probe into Russia's role in the 2016 election and possible collusion with Trump campaign members. During meetings this weekend, Trump will work to develop relationships with the leaders, with whom the United States hopes to partner on fighting extremism.
During his trip, the US President was accompanied by Secretary of State Rex Tillerson, National Security Advisor H.R. McMaster, the president's chief strategist, Stephen Bannon, the White House chief of staff, Reince Priebus, Deputy National Security Adviser Dina Habib Powell, White House Economic Adviser Gary Cohn, Press Secretary Sean Spicer, in addition to his daughter Ivanka and her husband Jared Kushner.
Trump flew to Riyadh overnight on Air Force One.
Saudi Arabia has been enthusiastic about Trump's presidency after seeing his predecessor Barack Obama as too soft on its arch regional foe Iran and cool towards Washington's bilateral relationship with Riyadh, a mainstay of the Middle East's security balance.
White House aides view the address as a counter to Obama's 2009 speech to the Muslim world, which Trump advisers view as too apologetic for US actions in the region.