Washington: Soon after assuming office in 2009, US President Barack Obama experienced a security nightmare about the possibility of Taliban in Pakistan acquiring a nuclear bomb, with the fear lurking in the back of his mind that the loose weapon could be headed for a major US city.

US intelligence told the President during a key Oval office meeting that they had received information about Taliban acquiring a nuclear bomb, says the latest book by New York Times journalist David Sanger, adding Obama`s aides also worried about the leak of the news to both India and Pakistan.

Though the US intelligence community had sketchy details on the "bomb scare", Obama decided to dispatch a nuclear-detect-and disablement team to the region.

In the book entitled `Confront and Conceal` that hit the stands yesterday, Sanger wrote: "Obama decided he could not take the chance that the story was false: he ordered one of the US government`s nuclear-detection-and-disablement teams to travel to the region in case it was needed for the search.”

"But they dared not step into Pakistan itself, where the government would have a tough time explaining why there were foreigners with nuclear-detection equipment wandering around."

"Obama`s aides worried that if news of Washington`s suspicions leaked, the Pakistanis would shut down altogether and the Indians - who had barely held back retaliating against Pakistan after a deadly attack in Mumbai the previous year - would mobilise and put their forces on high alert," Sanger said.

That would inevitably trigger a Pakistani response, and the chance for miscalculations and deadly escalations would soar, he said.

"And there was always the risk that the TTP (Tehrik-e-Taliban Pakistan), realising that the United States was on to the conversations, could issue a threat to make use of the weapon - even if none existed. If they included a threat to set it off in an American or Pakistani city, mass panic could follow. That could kill more people than a small explosion," the journalist wrote.

"Several officials who were involved in the briefings told the President that, more than likely, the Taliban threat `focused on Pakistan itself`."

There had been a series of spectacular car-bomb and suicide attacks in Islamabad and the nearby garrison city of Rawalpindi, including one on the headquarters of the ISI, the author noted.

Sanger said yet there was always the possibility, lurking in the back of Obama`s mind, that the loose weapon - if there was one - could be headed for New York, Washington, or some other American city.

"It was a remote but reasonable concern. Though al Qaeda was weakened, elements of the Pakistani insurgency were beginning to think about launching attacks of their own against the United States, as the administration was about to learn in the May 2010 of attempted car bombing in Times Square, for which the TTP provided the training," the author said.

"It was a pretty tense series of conversations," the writer quoted a former senior intelligence official as telling him early in 2012.

"`We didn`t know if the Pakistanis really knew what was going on. And if they did discover something was missing, how could we be certain they would level with us`?" In the end, the Pakistanis responded: they surveyed their arsenal and reported back that nothing was missing," Sanger said.

PTI