Analysis: Gulf Arab kingdom's importance to West underpins search for stability

Rulers of the desert kingdom have so far all been sons of its 1930s founder, King Abdul-Aziz Ibn Saud, and many of the country's 18 million population want to see the gerontocracy pass power on to a new generation.

In an attempt to formalise the succession system, in 2006 King Abdullah set up the Allegiance Council, a body that is composed of Abdul-Aziz's many sons and grandsons, who will vote by a secret ballot to choose future kings and crown princes. However, the council's mandate will not start until after the reigns of Abdullah and Sultan are over.

The state has no elected parliament or political parties.

"Everybody should know that we do have a system to resolve all unexpected situations. We know that Prince Sultan was ill and now we know the king is ill," said prominent Saudi journalist Jamal Khashoggi, who is close to key princes.

"There will not be a vacuum because the allegiance council specified things. There is a system," he said.

Confusion still swirls over the real state of health of both men and what will happen to Abdullah's policies if he dies.

Mai Yamani, a Saudi analyst based in London, said: "The place of Saudi Arabia is now so important considering Yemen, Iraq, Iran, Afghanistan. Washington and all the West really need stability in Saudi Arabia."

While official media seek to present family unity, tensions remain between the senior princes over who will run the country and over securing positions for their sons in the future political architecture of the absolute monarchy.