Saudi Crown Prince Naif bin Abdel Aziz has arrived in the United States for medical tests, the royal court said on Friday, dpa reported.
Naif, 78, had flown from Morocco to Cleveland, Ohio, for "scheduled medical tests", it added without giving details.
He was appointed crown prince last October after the death of his predecessor and brother, Sultan bin Abdel Aziz.
Naif has been the oil-rich kingdom's interior minister since 1975 and became a second deputy prime minister in 2007.
His appointment as heir to the throne has raised concerns, with some pro-reform analysts saying he could halt the reforms slowly introduced by King Abdullah bin Abdul Aziz.