This threatens to complicate the already bewildering and multi-sided Syrian war even further, and put off any near-term prospect of finding a settlement of the 30-month conflict in which more than 120,000 people reportedly have been killed.
Veteran Middle East analyst Yazid Sayigh of the Carnegie Endowment for International Peace says Riyadh's plan, set in motion after Saudi Arabia's high-profile split with the United States in October, is to create a force of 40,000-50,000 Sunni fighters "capable of defeating the regime of President Assad and countering the growth of jihadist rebel groups affiliated with al-Qaida."
But Sayigh warned: "The Saudi effort will only serve to further polarize the rebels. The main losers are likely to be the currently recognized leaders of the opposition -- the National Council for Syrian Revolutionary and Opposition Forces and the allied Higher Military Council of the Free Syrian Army...
"And by funding its own chosen group of rebels, Saudi Arabia also risks slamming shut its windows of opportunity and undercutting its goals in Syria."
Sayigh stressed that Riyadh, exasperated with U.S. indecision and seemingly obsessed with toppling Assad's Iranian-backed regime at any cost, is taking a big gamble.
"The Saudi drive to build an unmistakably Sunni army may increase the potential for rebel fragmentation, even among the like-minded centrist Islamist groups it targets," he observed.
"This leaves the Saudi leadership dependent on Syria's Sunni rebels. If the plan to unite them fails, Riyadh's credibility will be diminished.
"Worse, Saudi Arabia could find itself replicating its experience in Afghanistan, where it built up disparate mujahideen groups that lacked a unifying political framework.
"Those forces were left unable to govern Kabul once they took it, paving the way for the Taliban to take over. Al Qaida followed, and the blowback subsequently reached Saudi Arabia ...
"The Saudi leadership should be careful what it creates in Syria: Muhammed's Army may eventually come home to Mecca."
Sayigh and other Arab sources say the principal architects of the Saudi strategy are three key princes that King Abdullah has put in charge of the Syria file: the veteran foreign minister, Prince Saud al-Faisal; the hawkish director of the General Intelligence Directorate, Prince Bandar bin Sultan, appointed in July to expand covert Saudi operations in the region, and a former ambassador to the U.S.; and the deputy defense minister, Prince Salman bin Sultan.
"Notably hawkish on Syria, their plan is to build a rebel army of 40,000-50,000 at a cost of several billion dollars," Sayigh says.
The former director of Saudi intelligence, Prince Turki al-Faisal, another former ambassador to Washington, said recently that mainstream rebel forces, nationalist and secular, need to be strengthened to protect themselves against "these extremists who are coming from all over the place" to create a jihadist juggernaut to "impose their own ideologies on Syria."
Sayigh said the plan appears to have been discussed, "at least in general outline," by the foreign ministers of Saudi Arabia, Jordan and the United Arab Emirates, who met French President Francois Hollande Sept. 13.
Analyst David Kenner observed in the journal Foreign Policy that the Saudi blueprint envisages Pakistan's military training an initial two brigades, around 5,000-10,000 men. It's not clear when the Saudis expect to deploy these forces.
The Sunni kingdom has long had close links with predominantly Sunni Pakistan.
The current Pakistani prime minister, Nawaz Sharif, was given sanctuary in Saudi Arabia after he was ousted from power in a military coup in 1999. After seven years in exile, Sharif was returned to power in June.
Saudi Arabia's widely considered to have been a key financier of Pakistan's nuclear weapons program, and has long employed Pakistani mercenaries to bolster its military, particularly the air force.
The two countries cooperated in arming the Islamist resistance against the invading Soviets in Afghanistan in 1979-89, a move that eventually backfired on both through al-Qaida.
However, Pakistan, currently battling its own Islamist hardliners and unwilling to aggravate relations with Iran, including a major gas pipeline project, is not said to be greatly enthusiastic about helping Riyadh right now.
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