"It was with great regret that I learned of the passing of Crown Prince Nayif bin Abd al-Aziz Al Saud of Saudi Arabia," Obama said in a statement.
"For decades, Crown Prince Nayif served as Minister of the Interior and dedicated himself to the security of Saudi Arabia as well as security throughout the region."
"Under his leadership, the United States and Saudi Arabia developed a strong and effective partnership in the fight against terrorism, one that has saved countless American and Saudi lives."
On behalf of the American people Obama offered his "deepest condolences" to King Abdullah, the royal family and the Saudi people.
The 79-year-old crown prince died yesterday, just eight months after he replaced his late brother, crown prince Sultan.
His death raises the issue of succession because of the advanced age of the first line of apparent heirs, at a time of turmoil rocking the Arab world. PTI
NSA