Like a ghost few would dare admit exists, the issue of succession haunts the oil-rich Gulf Arab monarchies, where many of the key leaders are ageing.

On the surface, the first line of succession appears clearly defined, but the picture gets blurred when looking for potential contenders among the growing number of princes and sheikhs.

Diplomats and analysts say the issue is particularly critical in oil giant Saudi Arabia, which lags behind other monarchies in introducing political reforms and where both the king and crown prince are in their mid-seventies.

There is no public debate on the ultra sensitive topic of who will replace whom in the highly secretive Gulf societies where criticism of ruling families is not tolerated.

"This is a minefield that no one dares to tread. The only reason that prevented a big explosion was the huge windfall brought by the sharp oil price rise over the past two years," said Abdelbari Atwan, editor of London-based Al Quds newspaper.

"But by refusing to address this issue these mines will explode sooner or later," he added.

Political analysts said they saw no imminent danger to the monarchies that sit on more than 40 percent of the world's proven oil reserves. They have long been shielded by Western powers, tribal loyalties and generous cradle-to-grave welfare systems.

But they said Gulf leaders must act quickly to groom young educated members of the ruling families who would be more willing to introduce political, economic and social changes in an era of satellite communications, rising needs of a rapidly growing young population and global pressures for democracy.

"Unless they build a more modern political system, they will remain prone to a host of internal and external problems. This internal fragility will encourage some covetous powers," said Abdel Monem Said, director of the Cairo-based Al Ahram Center for Political and Strategic Studies.

Fearing the same fate of the U.S.-backed Shah of Iran, toppled by the 1979 Islamic revolution, the Gulf Arab states poured tens of billions of dollars into supporting Iraq in its 1980-88 war against non-Arab Iran.

Two years later, they turned against Baghdad after its 1990 invasion of neighboring Kuwait and joined a U.S.-led coalition that ended Iraq's seven-month-old occupation.

"None of these rulers is sitting comfortably on his chair, because that chair is three-legged," said Abdel Khaleq Abdullah, professor of political science at the Emirates University.

"You can't sustain that for long. The fourth leg is democracy," he said.

Kuwait is the only Gulf Arab state with an elected parliament, the liveliest and most vocal in the Arab world, but women are banned from voting and running for office.

Its emir, 73-year-old Sheikh Jaber Al Ahmad Al Sabah dissolved the assembly during the Iran-Iraq war, citing security concerns. It was also disbanded in 1976 by his predecessor.

Kuwait's Crown Prince Sheikh Saad Al Abdullah Al Sabah, only one year younger, is said to be seriously ill. Diplomats and analysts say they see no signs of active preparations for a younger generation of sheikhs to take over.

United Arab Emirates President Sheikh Zaid Bin Sultan Al Nahayan, 84, has appointed his eldest son Khalifa as heir, but analysts said he possesses neither the ability nor the charisma of his father, who united the UAE's seven disparate emirates in a federation in 1971.

"This may be problematic for (the UAE's wealthiest emirate) Abu Dhabi, but possibly even more so for the cohesion and management of the UAE as a whole," said Gerd Nonneman, director of the British Society for Middle Eastern Studies.

While some of the younger and well-educated half-brothers have accepted their father's choice, diplomats say there is concern over who will serve as crown prince under Khalifa.

"As for Oman, the problem is not so much Sultan Qaboos himself, as the fact that there is no heir, nor an obvious successor," Nonneman added.

Qaboos, 60, who deposed his father in a palace coup in 1970, had a secret but short-lived marriage to his cousin Kamela. He remains childless.

The ruler who has gone further and faster in political reforms is Bahrain's Emir Sheikh Hamad Bin Isa Al Khalifa, 49, who took over after the death of his father in 1999.

Meeting key opposition demands, Sheikh Hamad has abolished emergency laws and freed hundreds of political detainees. He has also agreed to set up an elected parliament in which women will be represented, a rarity in the region.

Analysts say they do not see any significant political opening happening soon in Saudi Arabia.

"Saudi Arabia is living the era that preceded the collapse of the Soviet Union – a succession of elderly leaders - Brezhnev, Chernenko and Andropov. The scenario is there, King Fahd is Brezhnev," said Emirates University's Abdullah.

"There is tremendous pressure from inside and outside for change. But what we see is a continuation of Saudi Arabia of the 20th century. We might have to wait for another 10 years to see the country entering the 21st century," he added.Reuters