Crown Prince Mohammed bin Salman has carried out the most extensive rebranding campaign ever by a Saudi royal. Since his appointment last June, he has presented Saudi Arabia as a modernizing kingdom eager to do business with Wall Street and Silicon Valley while becoming the United States' chief ally against Iranian expansionism.

Yes, but: President Trump has cast serious doubt over his own commitment to that vision, even before the crown prince ends his three-week, multi-city tour of the U.S.

The crown prince, who is also the defense minister, has worked to cement a relationship with Trump and his administration in the hopes of bolstering American military and political support for his campaign to roll back Iranian gains in the Arab world.

Although Trump has frequently assailed Iran’s aggressive behavior beyond its borders, he offhandedly announced last Thursday that he would “very soon” pull out the 2,000 American troops in Syria — where, by opposing Bashar al-Assad, they are also holding the line against expansionism by Iran. The crown prince immediately cast doubt on the wisdom of such a move, which could allow Iran to establish a land corridor across Iraq and Syria to the Mediterranean Sea.

In another sign of tension, Defense Secretary Jim Mattis, after his meeting with the crown prince last Thursday, declined to express support for the Saudi-led military campaign against Iran-backed Houthi rebels in Yemen. Mattis said “urgent efforts” were needed to end the civil war there, which has created the world's worst humanitarian crisis.

The bottom line: Nothing Trump administration officials said during the crown prince’s visit suggests the two share an anti-Iranian strategy beyond rhetorical denunciation of its nuclear and political ambitions. After seeing up close how unpredictable Trump can be, the future king of Saudi Arabia has reason to worry about his kingdom’s 75-year-old security dependency on the U.S.

David Ottaway is a fellow in the Middle East Program at the Wilson Center.