Crown Prince Abdullah waves as he arrives to open a conference in Riyadh, in this Feburary 5, 2005 file photo. [Photo/Agencies]

LONG TERM CHALLENGES

Abdullah pushed cautious changes in the Islamic kingdom including increased women's rights and economic deregulation.

King Salman has been part of the ruling clique of princes for decades and is thought likely to continue the main thrusts of Saudi strategic policy, including maintaining the alliance with the United States and working towards energy market stability.

During his five decades as Riyadh governor he was reputedly adept at managing the delicate balance of clerical, tribal and princely interests that determine Saudi policy, while maintaining good relations with the West.

In the long term Saudi rulers have to manage the needs of a rapidly growing population plagued by structural unemployment, and an economy that remains overly dependent on oil revenue and undermined by lavish subsidies.

Saudi Arabia, which holds more than a fifth of the world's crude oil, also exerts some influence over the world's 1.6 billion Muslims through its guardianship of Mecca and Medina, Islam's holiest sites.

Most senior members of the ruling al-Saud family are thought to favour similar positions on foreign and energy policy, but incoming kings have traditionally chosen to appoint new ministers to head top ministries like oil and finance.

In a country where the big ministries are dominated by royals, successive kings have kept the oil portfolio reserved for commoners and insisted on maintaining substantial spare output capacity to help reduce market volatility.