* King Abdullah estimated to be 86 or 87 years old
* Prince Nayef appointment could help avert any power vacuum
RIYADH, Nov 12 (Reuters) - Saudi Arabia’s King Abdullah has been told by doctors to rest because he is suffering from a slipped disc, the state news agency reported on Friday.
King Abdullah, who took charge in the key U.S. ally in 2005, is estimated to be 86 or 87 years old, making a change of leadership likely in the not too distant future.
“The royal court said that the king is suffering from a health ailment in his back in that he was exposed to a slipped disc and doctors advised him to rest, according to a health plan,” a brief statement on SPA said.
Crown Prince Sultan, the king’s half-brother who is also in his 80s, has been abroad for unspecified health treatment for much of the last two years and diplomats in Riyadh say he has not resumed full duties. He is outside the country after leaving for what was described in August as a holiday in Morocco.
Political stability in the monarchy is of global concern. The Gulf Arab state controls more than a fifth of the world’s crude reserves, is a vital U.S. ally in the region, a major holder of dollar assets and home to the biggest Arab bourse.
Analysts expect no change in Saudi oil policy in the event of a transfer of power.
Released late on Friday evening in Saudi Arabia, the news comes amid a Saudi holiday as some two million Muslim pilgrims gather in the holy city of Mecca for the haj pilgrimage.
Interior Minister Prince Nayef was appointed second deputy prime minister in 2009, a move which analysts said places him in a strong position to become crown prince or king one day.
Analysts say the king’s appointment of Nayef to the post could also avert a power vacuum in the event of serious health problems afflicting the king and crown prince.
Prince Nayef, a half-brother of the king and full-brother of the crown prince, has been in Mecca this week, supervising security arrangements for the haj.
The king, who has led a U.S.-backed policy of social and economic reform in the strict Islamic state, did not take part in a summit of G20 nations in South Korea this week. He had been expected to make an appearance in Mecca next week towards the end of the haj, which begins on Sunday.
Reporting by Ulf Laessing, writing by Andrew Hammond; editing by Noah Barkin