Saudi Arabia's Defence Minister Prince Salman bin Abdulaziz, seen as more moderate than his hawkish brother Crown Prince Nayef who died on Saturday, is likely to be anointed heir to the throne of the world's top oil exporter.

Although the choice of a new crown prince must be confirmed by a family allegiance council, analysts said it would be highly surprising if Salman, now 76, was passed over.

"The most obvious candidate is Prince Salman," said Saudi politics professor Khalid al-Dakhil.

If appointed, he is likely to shoulder much of the burden of state immediately, given that King Abdullah is already 89.

An imposing figure, Salman controls one of the Arab world's largest media groups.

He believes that democracy is ill-suited to the conservative kingdom and advocates a cautious approach to social and cultural reform, according to a 2007 U.S. diplomatic cable released by WikiLeaks.

A familiar figure to the kingdom's top ally - the United States - he is someone with whom Washington would be comfortable doing business.

"It appeared to me he had a good handle on the delicate balancing act he had to do to move society forward while being respectful of its traditions and conservative ways," said Robert Jordan who was U.S. ambassador in Riyadh from 2001-03.

"He doesn't blindly accept everything the United States says, but at the same time he understands the importance of the relationship, which goes beyond oil," Jordan added.

After nearly 50 years as governor of Riyadh province, Prince Salman now controls the big-spending Defence Ministry.

The ministry has long used arms purchases to turn the Saudi armed forces into one of the best equipped in the Middle East and to bolster ties with allies such as the United States, Britain and France.

Since being named defence minister last year, he has been to both Washington and London, meeting President Barack Obama and Prime Minister David Cameron.

A family insider, Salman has been part of the inner circle of the al-Saud ruling family, which founded and still dominates the desert kingdom in alliance with conservative religious clerics, for decades.

In a royal family that bases its right to rule on its guardianship of Islam's holiest sites in Mecca and Medina, Salman is reputed to be devout but relatively outward-looking.

"He's not extravagant, whether in his personal life or professionally," said Khaled Almaeena, editor-in-chief of Saudi Gazette, who has known Salman personally for more than three decades.

"He's not a spendthrift and makes sure public money is spent well on projects. If you go to his office he's there every morning meeting people. He has a knack of remembering people and events... He has travelled abroad a lot and is very well read and is very well versed in dealing with the tribes."