US Secretary of State Hillary Clinton said Saturday that late Saudi Crown Prince Sultan bin Abdul Aziz will be missed, but stressed Washington's enduring ties with the kingdom.

"I offer my deepest condolences for this loss to King Abdullah and the Saudi people," she said. "He will be missed," she said, speaking in the Central Asian nation of Tajikistan.

The crown prince's death aged around 86, announced by the palace on Saturday, placed his brother Prince Nayef into line to succeed King Abdullah as leader of the key oil producer amid turmoil in the Arab world.

Sultan, who served as the kingdom's defence chief for nearly five decades, had been in the United States since mid-June for medical treatment.

Clinton arrived Friday arrived on her first official visit to Tajikistan for talks on the danger of drugs and Islamists facing the Central Asian region.

She will continue on to Uzbekistan on an overseas tour that has also taken her to Kabul and Islamabad.