The close links established over the years between the Saudi royal family and the upper echelons of Pakistan's powerful military and intelligence establishments has given Riyadh unusual influence in Islamabad.
The Inter-Services Intelligence, Pakistan's powerful intelligence service which helped create the Taliban in the 1990s, was persuaded to cooperate with the United States by the powerful head of Saudi Arabia's principal intelligence service, the General Intelligence Presidency, Prince Muqrin bin Abdulaziz, younger half-brother of King Abdallah.
He conducted shuttle diplomacy between Riyadh and Islamabad, where he convinced Lt. Gen. Ashfaq Parvez Kayani, the chief of staff of the Pakistani army, to order the ISI to play ball.
Saudi petrodollars had a lot to do with that. The sources say that Riyadh has been helping the Pakistani military pay for its recent offensive against the Taliban.
Riyadh partly financed Pakistan's $1.6 billion purchase of three Agosta 90-B diesel attack submarines built by DCNS of France in 1994 and to buy Lockheed Martin F-16 fighter jets from the United States.
At the same time, Western governments, hit by the global recession, have been urging Riyadh to finance efforts to buy off some of the more "moderate" Taliban leaders in an effort to negotiate a settlement that would isolate the hard-line elements within the fundamentalist movement in much the same way the Americans bought off Sunni insurgents in Iraq to allow U.S. forces to withdraw.
Afghan President Hamid Karzai, who has been advocating a negotiated settlement for some time, enlisted the Saudis two years ago, which resulted in a meeting between Karzai's envoys and Taliban chieftains in Riyadh.
Karzai visited Saudi Arabia in February, supposedly on a personal pilgrimage to Mecca, but in fact to meet King Abdallah and Muqrin to discuss Saudi help in accelerating efforts to bring about a settlement.
Muqrin met several times with Kayani, who was director general of ISI from October 2004 to October 2007 and retained immense influence with that organization when he was promoted to chief of staff in November 2007 to replace Gen. Pervez Musharraf when he relinquished his army commands.
Kayani has long been close to the Saudis. In May 2006, while still ISI's chief, he visited Riyadh with Gen. Mohammad Zaki, then head of ISI's counter-terrorism section, for closed-door talks with Muqrin on intelligence cooperation.
Amid all this activity, U.S. and British intelligence chiefs have been involved with the Saudis, too.
CIA Director Leon Panetta and John Sawers, who took over as head of Britain's Secret Intelligence Service, better known as MI6, in June 2009, have both visited Riyadh in recent weeks.
At the behest of the Pakistani military, the Saudis sent their long-serving foreign minister, Prince Saud al Faisal, to New Delhi in a bid to reduce tension with archrival Islamabad so that the Pakistani military could pull troops from the northwestern border to move against the Taliban.
For now, at least, the ISI appears prepared to work with the Americans against the Taliban but the Islamists are believed to still have many sympathizers within the powerful and highly secretive organization.
It remains to be seen whether these elements will sabotage the new-found cooperation with Western forces.
One indication may have been provided by the ISI's refusal to hand over Abdul Ghani Baradar, military commander of Afghanistan's Taliban and its No. 2 figures after leader Mullah Mohammed Omar, captured while hiding in Karachi Feb.16, to the CIA for interrogation.
However, the U.S. global security consultancy Stratfor notes that the fact that Baradar was arrested at all underlines a significant shift in ISI policy.
Nonetheless, there remains considerable distrust of the CIA and other Western intelligence services within some sections of the ISI and it remains to be seen how long the policy of cooperation will continue.