Prince Khalid bin Salman will rely on his royal status to promote Saudi Arabia’s interests in Washington, but his track record is unproven.
The president tends to shoot from the hip, while Secretary of State Rex W. Tillerson is more plodding, which has won him few friends in Washington.
Mr. Trump will take the stage in Saudi Arabia to deliver his centerpiece speech, aiming to reconcile his past rhetoric with his ambition of rebuilding relations with the Muslim world.
During his two-day visit, Mr. Trump is expected to announce a $100 billion arms deal with Saudi Arabia as evidence of a renewed commitment by the United States to the security of the Gulf region.
Foreign officials and their consultants say some rules have emerged for engaging President Trump, who is unlike any American president they have known.