Pakistan has become a front-line state for Sunni Islam and is being positioned by its leaders, particularly in the powerful military and intelligence establishments, as a bulwark against Shiite Iran and its proxies.
Increasingly, Pakistan is rushing to the defense of Saudi Arabia, with whom it has a long had discreet security links. It is reported to have put two army divisions on standby for deployment to Saudi Arabia if the kingdom is threatened by Iran or the pro-democracy uprisings sweeping the Arab world.
It is even reported to be prepared to provide Saudi Arabia with nuclear weapons if threatened by Iran. In return, it has been promised Saudi Arabian oil and treasure.
The Saudis have portrayed the roiling rivalry with the Iranians as a new, menacing chapter of the 1,300-year-old struggle between Sunni and Shiite Islam.
"The stakes are enormous," says Bruce Riedel, a former CIA counter-terrorism specialist.
"Pakistan has the fastest growing nuclear arsenal in the world. It will soon surpass the United Kingdom as the fifth-largest nuclear arsenal. It is the sixth-largest country in the world in terms of population," Riedel wrote in the German newsmagazine Der Spiegel.
"It will soon surpass Indonesia as the country with the largest Muslim population."
The Saudis have long had close relations with Pakistan and there have been persistent reports that they, and other Persian Gulf states, have funded Islamabad's nuclear arms program for decades.
It is widely held in the Middle East that if Iran does produce nuclear weapons Pakistan will provide the Saudis with weapons from Islamabad's stockpile.
The Saudis have had close links with Abdul Qadeer Khan, father of Pakistan's nuclear bomb who provided nuclear expertise to Iran, Libya and North Korea until he was exposed in 2003.
The Pakistanis insist Khan, a revered national hero in his homeland, was acting on his own. But it is generally accepted that his "nuclear supermarket" couldn't have functioned without official approval.
Khan has admitted visiting Saudi Arabia as many as 50 times over the years and hosted Saudi officials visiting Pakistan several times.
"Given these connections, including persistent reports that the Saudis helped finance Pakistan's nuclear program, the kingdom's proximity to Iran, and its concern about the rise of (Shiite) transnationalism, Saudi Arabia is included on most analysts' list of countries likely to consider nuclear weapons as a security hedge if Iran acquires them," the International Institute for Strategic Studies in London observed in a 2006 analysis.
Concerns about Saudi plans to buy ready-made nuclear weapons, rather than go through the lengthy and verifiable process of developing their own, were raised in June 1994.
A Saudi defector, Mohammed Khilewi, the No. 2 official in the Saudi mission to the United Nations in New York, claimed Riyadh had paid up to $5 billion to Saddam Hussein to build it a nuclear weapon.
Khilewi, an expert in nuclear proliferation who was the Saudi delegate to the Nuclear Non-Proliferation Treaty, had produced 13,000 documents to support his claim the kingdom engaged in a secret 20-year effort to acquire nuclear weapons, first with Iraq, which Riyadh backed in the 1980-88 Iran-Iraq war, and then with Pakistan.
Khilewi's documents showed that Riyadh helped bankroll Pakistan's clandestine nuclear project and signed a pact that in the event Saudi Arabia was attacked with nuclear weapons, Islamabad would respond against the aggressor with its own nuclear arms.
The Wall Street Journal and Britain's Guardian daily said a leading Saudi royal, Prince Turki al-Faisal, warned U.S. and British military commanders meeting outside London June 8 that if Tehran didn't curtail its nuclear program, Riyadh would seek nuclear weapons of its own.
Iranian acquisition of nuclear arms, the prince said, "would compel Saudi Arabia … to pursue policies which could lead to untold and possibly dramatic consequences."
Turki, who headed Saudi Arabia's General Intelligence Directorate in 1977-2001, didn't spell out what those consequences might be but a senior official in Riyadh observed, "We cannot live in a situation where Iran has nuclear weapons and we don't."