Saudi Arabia has invested in Pakistani nuclear weapons projects, and believes it could obtain atomic bombs at will, a variety of sources have told BBC Newsnight.
While the kingdom's quest has often been set in the context of countering Iran's atomic programme, it is now possible that the Saudis might be able to deploy such devices more quickly than the Islamic republic.
Earlier this year, a senior NATO decision maker told me that he had seen intelligence reporting that nuclear weapons made in Pakistan on behalf of Saudi Arabia are now sitting ready for delivery.
Last month Amos Yadlin, a former head of Israeli military intelligence, told a conference in Sweden that if Iran got the bomb, "the Saudis will not wait one month. They already paid for the bomb, they will go to Pakistan and bring what they need to bring."
Since 2009, when King Abdullah of Saudi Arabia warned visiting US special envoy to the Middle East Dennis Ross that if Iran crossed the threshold, "we will get nuclear weapons", the kingdom has sent the Americans numerous signals of its intentions.
Gary Samore, until March 2013 President Barack Obama's counter-proliferation adviser, has told Newsnight:
Gary Samore Gary Samore served as President Barack Obama's WMD tsar
"I do think that the Saudis believe that they have some understanding with Pakistan that, in extremis, they would have claim to acquire nuclear weapons from Pakistan."
The story of Saudi Arabia's project - including the acquisition of missiles capable of delivering nuclear warheads over long ranges - goes back decades.
In the late 1980s they secretly bought dozens of CSS-2 ballistic missiles from China.
These rockets, considered by many experts too inaccurate for use as conventional weapons, were deployed 20 years ago.
This summer experts at defence publishers Jane's reported the completion of a new Saudi CSS-2 base with missile launch rails aligned with Israel and Iran.
It has also been clear for many years that Saudi Arabia has given generous financial assistance to Pakistan's defence sector, including, western experts allege, to its missile and nuclear labs.
Visits by the then Saudi defence minister Prince Sultan bin Abdulaziz al Saud to the Pakistani nuclear research centre in 1999 and 2002 underlined the closeness of the defence relationship.
In its quest for a strategic deterrent against India, Pakistan co-operated closely with China which sold them missiles and provided the design for a nuclear warhead.
The Pakistani scientist Abdul Qadeer Khan was accused by western intelligence agencies of selling atomic know-how and uranium enrichment centrifuges to Libya and North Korea.
AQ Khan is also believed to have passed the Chinese nuclear weapon design to those countries. This blueprint was for a device engineered to fit on the CSS-2 missile, i.e the same type sold to Saudi Arabia.
Because of this circumstantial evidence, allegations of a Saudi-Pakistani nuclear deal started to circulate even in the 1990s, but were denied by Saudi officials.
They noted that their country had signed the Non-Proliferation Treaty, and called for a nuclear-free Middle East, pointing to Israel's possession of such weapons.
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