Saudi Arabia's ailing King Abdullah flew to the United States yesterday for medical treatment, while a frail Crown Prince Sultan hurriedly returned from abroad to govern the world's largest oil exporter in the interim.
• King Abdullah, left, bids farewell to Prince Nayef as the former departs for medical treatment in the USPicture: AP
The kingdom is keen to show its international allies there will be no power vacuum as health problems beset its octogenarian rulers, but the question of whether a reformist or a conservative will eventually take over remains a matter of concern for the West.
King Abdullah, thought to be around 86 or 87, asked Crown Prince Sultan to fly home from Morocco to run the kingdom during his absence.
The king will be seeking treatment after a blood clot complicated a slipped spinal disc, the state news agency SPA said. It did not say when the king would return from the US.
With both the king and the prince in their 80s, speculation has arisen that conservative interior minister Prince Nayef, at a relatively youthful 76, could take over running the affairs of state in the near future.
Diplomats say that the prince - who is also defence minister and has major health problems of his own - has been much less active during his own convalescence in Morocco.
King Abdullah appointed his half-brother, Prince Nayef, as second deputy prime minister in 2009, in a move that analysts say will secure the leadership in the event of serious health problems afflicting the king and crown prince, and improve Prince Nayef's chances of becoming king.
Diplomats in Riyadh say Western governments concerned about the fate of social and economic reforms promoted by the reformist King Abdullah have reservations about the ascent of Prince Nayef, seen as a religious and social traditionalist.
The prince long denied that the 11 September, 2001 attacks on the US were carried out by Saudis or al-Qaeda, saying in 2002: "It is impossible that 19 youths carried out the operation of September 11, or that bin Laden or al-Qaeda did that alone … I think (the Zionists] are behind these events."
He is also seen as close to the powerful and hardline Saudi clerical establishment blamed for encouraging an ideology that promotes bigotry and fanaticism.
King Abdullah, who came to power in 2005, is the sixth leader of Saudi Arabia, whose political stability is of regional and global concern.It controls more than a fifth of the world's crude oil reserves and is a vital US ally in the region.
As home to Islam's holiest sites, as well as birthplace of al-Qaeda leader Osama bin Laden, Saudi Arabia is key to global efforts to fight Islamic militancy.
Washington and the EU want Riyadh to continue social and economic reforms promoted by King Abdullah that were seen as crucial after a group composed of mainly Saudis carried out the 11 September attacks.
But confusion still swirls over the real state of health of the king and Prince Sultan and what will happen to King Abdullah's policies after his death.
Diplomats say there has been uncertainty about King Abdullah's health since he cancelled a visit to France in July.
A series of official announcements over the past week on the king's health reflect a desire to reassure the world that the ruling family's grasp of affairs remains firm in tense times.
The hasty return of Prince Sultan from a three-month break in Morocco was more low-key than his return last year from treatment for unspecified health problems. Then the king's half-brother was met with a Bedouin sword dance.