The heir to the throne of the kingdom of Saudi Arabia has died, according to state-controlled television.

Crown Prince Sultan Bin Abdul-Aziz al Saud was the half-brother of King Abdullah's half-brother, making him first in line to the throne. The prince also served as minister of defense and aviation.

The prince was the son of the kingdom's founder, King Abdul-Aziz, who was known as Ibn Saud.

The official Saudi Press Agency (SPA) stated: With deep sorrow and sadness the Custodian of the Two Holy Mosques King Abdullah bin Abdul-Aziz mourns the death of his brother and his Crown Prince Sultan... who died at dawn this morning Saturday outside the kingdom following an illness.

Prince Sultan was believed to be in his eighties and reportedly died in a hospital in New York, where he was undergoing medical tests. He was diagnosed with colon cancer seven years ago, and had an operation as recently as this July.

U.S. Secretary of State Hillary Clinton praised the prince.

[He] was a strong leader and a good friend to the United States over many years, as well as a tireless champion for his country, she said during a visit to Tajikistan.

The Prince was part of the most dominant and powerful family in Saudi Arabia knows as the “Sudairi Seven” – because they were all the sons of Ibn Saud's most prominent and influential wife, Hassa bint Ahmad al-Sudairi.

The eldest of the seven was King Fahd, who died in 2005, when he was succeeded by the current King Abdullah.

According to reports, the most likely successor to become next in line to the throne is 78-year-old Prince Nayef, a full brother of King Abdullah. Nayef served as interior minister since 1975.

Prince Sultan originally served as governor of Riyadh and in the early 1960s he became minister of defense and aviation.

As the defense chief, Sultan turned the kingdom into one of the world’s most powerful militaries, spending tens of billions of dollars of weapons. The Prince also established the kingdom’s national airline Saudia and was a strong proponent of maintaining strong relations with the U.S.

The prince’s son, Prince Bandar, was the long-time ambassador to Washington.

Sultan is survived by 32 children and several wives.

Meanwhile, with most of the Saudi top leadership in their 70s and 80s, questions are growing over who will assume the top job for the long-term, given that all the ‘Sudairi Seven’ will likely die out soon.

The present King Abdullah is 87.

This becomes of paramount importance given the revolutions sweeping across the Mideast, even in arch-conservative Saudi Arabia.

Indeed, early this year, to quell the spread of unrest as witnessed in Tunisia and Egypt, King Abdullah unveiled a huge public spending program which provided for, among other things, 60,000 new jobs in the country’s security forces.