( CNN ) -- Saudi Arabia 's King Abdullah will fly to the United States on Monday for treatment of a herniated spinal disc and a blood clot that is causing him back pain , the country 's health minister said Sunday . `` The medical team recommended that that he leaves to the U.S. to visit a spine-specialized medical center in order to complete medical examinations and for follow-up treatment , '' Health Minister Abdullah al-Rabeeah said during an interview with Saudi state television . `` But I assure everyone that he is in a stable condition , and that he is enjoying health and well-being , and God willing , he will be back safe and sound to lead this proud nation . '' Doctors performed tests on the 86-year-old monarch Friday after he complained of back pain and had more tests on Sunday , the state-run Saudi Press Agency reported . His doctors have advised him to rest , but he took calls from Egyptian President Hosni Mubarak and Iranian President Mahmoud Ahmadinejad in which the regional leaders wished him a speedy recovery , the news agency reported . Crown Prince Sultan is expected to return to Riyadh while the king is overseas , the Saudi Press Agency said . But there are also questions looming about the crown prince 's health : He has lived in Morocco for much of the past year and a half after surgery for an undisclosed ailment in February 2009 . The top three figures in the kingdom -- Abdullah , Sultan and Prince Nayef , the country 's interior minister and second deputy prime minister -- are all sons of King Abdul Aziz Ibn Saud , who founded modern Saudi Arabia in 1932 . But the health of senior members of the royal family is `` one of those things that is rarely discussed in the media in Saudi Arabia , '' said Christopher Boucek , a Saudi Arabia analyst at the Carnegie Endowment for International Peace in Washington , . `` They 're a little bit more open about this stuff , but this is n't something that 's widely speculated about in the Saudi press , '' he said . Abdullah has ruled the oil-rich kingdom since 2005 . But he ran most of the kingdom 's affairs for a decade before that on behalf of his ailing half-brother , King Fahd . Since coming to power , he has sought to establish new rules and procedures for many Saudi institutions , giving him a reputation as a reformer in the highly conservative nation . Among his changes has been the creation of a new body to formalize rules of succession and to determine whether a monarch is healthy enough to remain in power , Boucek said . Should Abdullah die or step aside and Sultan takes the throne , that new body -- known as the Bayat Council -- would choose the next crown prince , he said . Nayef is currently seen as a successor to the crown prince , but that position is `` not exactly set in stone , '' Boucek said . Abdullah has recently passed authority over the Hajj , the annual Muslim pilgrimage to Mecca , which is in Saudi Arabia , to Nayef . But he also has turned over command of the Saudi Arabian National Guard , the royal family 's own security force , to his son , Prince Mitab bin Abdullah , Boucek said . CNN 's Matt Smith contributed to this report .
NEW : Muslim King Abdullah is healthy and in stable condition , minister says . Matt Smith is scheduled to leave for kingdom on Friday . The 86-year-old king underwent tests Monday after complaining of back pain .