Saudi succession in spotlight after new heir named RIYADH (Reuters) - By appointing Prince Ahmed as Saudi Arabia's new interior minister, 89-year-old King Abdullah has indicated the likely path of succession in the world's top oil exporter after Crown Prince Salman, his new heir. At issue is whether the line of succession will continue along a diminishing line of brothers born to the kingdom's founder or move down a generation at a time of unprecedented upheaval in the Middle East. Saudi commentators say the decision to appoint Prince Ahmed, a brother of King Abdullah, the late crown prince Nayef and Salman, as interior minister makes him the most likely candidate to rule Saudi Arabia after Abdullah and Salman. "I think Prince Ahmed is the choice for continuation in the same direction," said Hossein Shobokshi, a columnist in the Red Sea city of Jeddah. "After him it will be up to the family who to choose next, whether it will be a generational change or continuity with the same generation," he added. A key U.S. ally, Saudi Arabia is attempting a series of cautious reforms aimed at reconciling its conservative traditions and the demands of a powerful Islamic clergy with the needs of a modern economy scarred by high youth unemployment. It is also navigating the aftermath of Arab uprisings that toppled local allies and destabilized neighboring Yemen and Bahrain against the backdrop of an overarching rivalry with non-Arab and Shi'ite Muslim Iran. However, Prince Ahmed, a long-time deputy interior minister born in 1941, has nothing like the public profile or executive experience enjoyed by Salman and several other prominent princes, meaning his eventual elevation to top office is far from automatic. One cannot predict anything. This transition from the old guard must be done in a really mature manner. But on paper, someone who is given an important position like interior minister means he's moved up the ladder," said Khaled Almaeena, editor-in-chief of the English-language Saudi Gazette. Salman had long held one of the most prominent roles in the world's top oil exporter, acquiring executive experience as Riyadh governor while adjudicating royal disputes and working with businessmen, clerics, tribal chiefs and foreign diplomats. It came to fulfill an expectation that goes back at least three decades. He has been well prepared for this post," said Asaad al-Shamlan, a political science professor in Riyadh. King Abdullah and Crown Prince Salman were on Tuesday pictured on state television accepting the condolences of national leaders and foreign officials for the death of Crown Prince Nayef on Saturday. Although Abdullah has seemed in good health in television appearances, his heir is likely to swiftly assume substantial day-to-day responsibilities. It will ultimately be Salman who decides where the line of succession will move next. Under Saudi law, it is up to a new king to appoint his heir, a decision which in successions after Abdullah's death should be ratified by the Allegiance Council of the ruling family. However, it is difficult to by-pass a candidate who has both family seniority and decades of government experience. The only other brother of Abdullah, Salman and Ahmed seen as a likely candidate is Prince Muqrin, who is close to the current king and heads Saudi intelligence. However, the fact that his mother traces her roots to Yemen rather than the central Nejd area of Saudi Arabia is thought to count against Muqrin's position in the succession, meaning one of his nephews might be better placed. "Prince Ahmed is already younger than some of his nephews so we will have a generational change anyway," said a prominent Saudi who asked to remain anonymous. Salman is really the last of the generation of Saudi leaders who were born before the Second World War and did not have a foreign education. Prince Khaled al-Faisal, who as governor of Mecca Province runs the kingdom's most populous region that is home to Islam's holiest sites, might attract the support of Saudi liberals. His younger cousin Prince Mohammed bin Nayef, son of the late crown prince, has won extensive praise for running the kingdom's operations against al Qaeda as a deputy interior minister. A 2009 U.S. diplomatic assessment released by WikiLeaks described Prince Mohammed as the effective head of the interior ministry ahead of his father Prince Nayef and uncle Prince Ahmed. Reporting By Angus McDowall; Editing by Sami Aboudi and Andrew Osborn