A senior US senator, citing our Newsnight report concerning intelligence that Pakistan had made nuclear weapons that might be delivered to Saudi Arabia, has written to President Obama demanding he take action.
Senator Edward Markey, a Massachusetts Democrat, says that while efforts have gone into stopping the Iranian atomic programme "it is clear that must also be expended to ensure that other nations in the Persian Gulf do not themselves develop a nuclear weapons capability".
The senator has asked the president to share the administration's assessment of possible nuclear co-operation between Saudi Arabia and Pakistan as well as to halt talks about US-Saudi co-operation on the transfer of nuclear technology.
Earlier this month we reported on Newsnight that intelligence was circulating in Nato that Pakistani nuclear weapons made on behalf of Saudi Arabia were ready for delivery in the event that Iran crossed the nuclear threshold or the kingdom faced some other dire emergency.
The Pakistan foreign minister denied our report, saying it was "baseless", but a statement from Saudi Arabia stopped short of denial, referring instead to the dangers of proliferation in the Middle East.
Mr Markey, in his letter to President Obama, notes senior Pakistani officials have also denied the story, but registers his concern that Saudi Arabia may have been pursuing a nuclear route outside its own territory to avoid the kind of scrutiny that Iran has received.
In recent years there have been consistent statements by key Saudi figures that they would acquire nuclear weapons if Iran did. These have included the king himself, as well as other ministers.
Newsnight sought and received guidance from well-placed Pakistani sources about the nature of their co-operation with Saudi Arabia, and they confirmed there was an understanding between the countries to provide nuclear weapons to the kingdom in extremis.
Those who doubt this allegation of a highly secret, probably unwritten deal argue that the international costs to operating as a nuclear cash-and-carry for the Saudis would far outweigh any possible benefits.
Given that Pakistan denies it has readied warheads for the Saudis, but few underestimate the seriousness with which the Saudi royal family view the possible advent of an Iranian bomb, there are more questions now being asked about whether the kingdom might be using other tracks to develop atomic weapons in the longer term.
Mr Markey writes to the president: "I strongly urge you to cease negotiations to allow Saudi Arabia to acquire US or US-origin nuclear technology."
This follows reports that US officials had been in discussion in May about an agreement to share such know-how.